Alright, here's my promised long post. The goal of this post is not to convince you that Mega Lucario is not uber. I don't think I can single-handedly convince everyone that Mega Lucario isn't uber so he won't get banned. Rather, the goal of this post is to convince the reader that the argument against Mega Lucario isn't as strong as it's normally thought, and that it's completely unwarranted for the people here to think that it's a one-sided argument. Rather, I think it's an argument with equally strong sides for both uber and non-uber proponents.
As you all know, there are 3 characteristics to consider before naming a Pokemon "uber." Smogon defines these characteristics as follows:
Offensive Characteristic: A Pokémon is uber if, in common battle conditions, it is capable of sweeping through a significant portion of teams in the metagame with little effort.
Defensive Characteristic: A Pokémon is uber if, in common battle conditions, it is able to wall and stall out a significant portion of the metagame.
Support Characteristic: A Pokémon is uber if, in common battle conditions, it can consistently set up a situation in which it makes it substantially easier for
other pokemon to sweep.
Now there's a mistake in these definitions in that one is supposed to use
"if and only if" instead of "if" for definitions, but that's not really relevant on Smogon. What is relevant is that Mega Lucario fits into one of these characteristics. It's obviously not the defense characteristic since he has really poor defensive stats: have you ever seen a RestTalk Lucario? The other two characteristics, on the other hand, are significant. The offense characteristic is the one I will be discussing the most throughout this post, since Lucario is generally used as a lategame sweeper, though he can be used to open holes in the opponent's team for other sweepers as well. By discussing the offense characteristic we can understand whether or not he fits into the support characteristic for uber Pokemon as well.
Mega Lucario--who gets STAB for Steel and Fighting type moves--has 145 base attack and 140 special attack, along with 112 base speed, and decent enough bulk to survive most attacks. His ability is probably what has caused people to consider him uber: Adaptability, which increases STAB to 2x instead of 1.5x. This means that Close Combat does significantly more damage compared to LO Lucario: in addition to not losing health after every damaging move, he also does a lot more damage due to his higher attack stat and Adaptability. For the sake of comparison, Mega Lucario does at least 144% damage against the most common Blissey whereas LO Lucario can only manage 115% against the same Blissey. Adaptability is one of the two main reasons people consider him uber.
But Mega Lucario is an extremely strong special sweeper as well. At 140 base special attack, a number comparable to his base attack, he has even fewer counters as a special sweeper, though he generally does a lot more damage as a physical sweeper. Nasty Plot can be used to deceive the incoming Landorus-T or Gliscor and you can OHKO them with Flash Cannon, or hit another incoming Pokemon really hard with it. Lucario's unpredictability is easily the second of the two main reasons he is considered uber. I don't think that Adaptability is as impressive as people think it is; I'm convinced that if he is to be considered uber at all, it's due to the second reason, his versatility.
Some have taken issue with what I define as checks and counters. For the sake of simplicity, I'll go with Smogon's definition of both. There are some issues with these definitions, but I'll accept them as true.
Pokémon A
checks Pokémon B if, when Pokémon A is given a
free switch into Pokémon B, Pokémon A can win every time, even under the worst case scenario, without factoring in hax.
Pokémon A
counters Pokémon B if Pokémon A can
manually switch into Pokémon B and still win every time, even under the worst case scenario, without factoring in hax.
Notice that going by these definitions, Pokemon like Charizard have no counters. This is because there is no one Pokemon who can switch
Let's list and consider each one:
Checks to most sets:
Talonflame (he can take a hit from ES at full health, and he can take a hit from BP and VW after SR)
Genesect (with the exception of Vacuum Wave sets
Greninja (he can take a hit from both ES and BP, but not VW)
Conkeldurr
Breloom
Starmie (can take a hit from ES in additon to VW and BP)
A bunch of Scarf users, ranging from Garchomp, Rotom-W, Heatran, and so on.
You'll notice that a lot of these depend on Vacuum Wave. That is why I said check to "most" sets. If Lucario goes with Vacuum Wave, he's going to be a victim of Talonflame. If Lucario goes for ExtremeSpeed or Bullet Punch, he'll still be unable to deal with Genesect. No matter what move you go with you're still screwed against a check one way or another. Bu since only 32% of Lucarios have Vacuum Wave, you can generally use Genesect against him--and you can certainly use Genesect against him if he uses SD. You can always use Talonflame against him if he uses NP. No matter what priority move Lucario chooses there will be many reliable checks to deal with him.
Cripplers:
Sableye
Klefki
Thundurus
Salamence
Manectric
Landorus-T
All these Pokemon are ones who can somehow paralyze him, or lower his attack, preventing a sweep. Lucario isn't very good if he's paralyzed, and if you have an Intimidate user, you can try to play around him by Intimidating him until you can get a nice hit on him. These may not be checks or counters but they're still worth mentioning.
SD Lucario w/ Ice Punch:
Aegislash
Mega Venusaur (Sleep Powder)
Jellicent
Bulky Gyarados
Bulky Zapdos
Bulky Moltres
Bulky Volcarona
Aegislash is a solid counter to SD Lucario with Ice Punch. Aegislash can even take a hit from SD Crunch Lucario, though, so death is not guaranteed if you get the prediction wrong here. Mega Venusaur with Sleep Powder is a decent counter to every single variant of Mega Lucario, as are Bulky Gyarados, Zapdos, Moltres and Volcarona. Jellicent can burn Lucario with Ice Punch with no problems and take a hit from even SD Crunch Lucario.
SD Lucario w/ Crunch:
Aegislash (with good play)
Gliscor
Mega Venusaur (Sleep Powder)
Bulky Gyarados
Landorus-T
Bulky Zapdos
Bulky Moltres
Bulky Volcarona
You aren't guaranteed to take on Aegislash if you use Crunch here. I consider it a bad idea to use Crunch for a few reasons: the only reason you want Crunch is for Aegislash, who has King's Shield! It's not even guaranteed you'll win for certain. On the other hand, you will win for certain against Landorus-T and Gliscor. I think it's pretty clear that Crunch is an inferior choice, but it is still worth considering. You are now countered by Gliscor and Landorus-T as well. It's clear that this set has some hard counters.
NP Lucario w/ Dark Pulse, Flash Cannon, Aura Sphere:
Bulky Gyarados
Mega Venusaur
Bulky Zapdos
Bulky Moltres
Volcarona
This set has few real counters, but it has more checks than usual due to having no priority moves. For example, Alakazam, Talonflame, Genesect and so on all have an easy time against him.
NP Lucario w/ Vacuum Wave over Dark Pulse:
Aegislash
Bulky Gyarados
Mega Venusaur
Bulky Zapdos
Bulky Moltres
Bulky Volcarona
This set has some advantages; it can't be checked by Genesect and Scarf Heatran, for example. Unfortunately Dark Pulse is handy against Aegislash, who can't use King's Shield against you. I'm not going to consider Lucario with Vacuum Wave over Aura Sphere. He can't get past the most common Pokemon in the game, Rotom-W (who usually sports Calm nature with 252 SpD EVs according to usage).
What do we have to learn from these considerations? It's true that Mega Lucario is ridiculously strong thanks to Adaptability, but surprisingly enough, he still has some pretty good counters in the OU metagame. This is due to a phenomenon known as the "four moveslot syndrome" or 4MSS for short. Since the reason Mega Lucario is so dangerous is generally due to Swords Dance or Nasty Plot, if he picks one move over another, a lot more things can counter him. If he doesn't have a priority move, he's checked by a lot more things. If you go with Crunch over Ice Punch, he's countered by more things. And so on. So Adaptability is not that much of an issue, though I grant he wouldn't be uber without it. What really is an issue is his unpredictability.
Another observation is that each given Lucario set has many counters: it's his unpredictability that makes him so dangerous. And I agree; I think it's a problem that the opponent has to play the guessing game with Lucario when he comes in. But think of it like this: Charizard might be even more unpredictable than Lucario is, but no one thinks he's uber. You have to play the guessing game whenever Charizard comes in, and he has no solid counters for both of his sets at the same time. Is Charizard uber? Of course not. So just because a Pokemon has no counters for both sets at the same time, it doesn't mean they're uber.
You'll also notice that many of these counters are weak to Stealth Rock. This is because Fighting's resists, Flying and Bug, are both weak to SR. These Pokemon who can counter Lucario are Zapdos, Moltres, Volcarona and Gyarados. It's generally assumed by most of the debaters here that SR will always be up, with no cost whatsoever. This is naive to say the least. In real competitive play at a high level, SR is not that easy to set up for multiple reasons:
1. It can cost 2 turns to set up SR if you start the match with your SR lead: one to use SR and one to switch out. If you don't start with your SR lead, it costs 3 turns: one to switch in, one to use SR, one to switch out. The best time to use SR is when, for example, you bring in SR Heatran into Talonflame. Then it only really costs one turn, but this may not always happen.
2. One word: Defog. SR isn't as big of a threat as it used to be in the previous generations, since a lot of teams nowadays pack Defog. If the opponent manages to use Defog, you'll need to take a few turns to use SR again for your Mega Lucario's sweep.
These turns you lose using SR are precious. You lose momentum when you could have been doing something else, and in some cases, if your opponent keeps up the offensive pressure, you might not even be able to set up SR at all. Furthermore, some have argued that Defog + Rapid Spin costs the same amount of turns. This is true, but this doesn't detract from the point that SR has costs. I am merely making the claim that SR cannot be taken for granted as everyone thinks it can be here.
Another reason why Moltres, Volcarona, Zapdos and Gyarados do make good counters to Lucario is that you'll generally want to use Defog and/or Rapid Spin along with them. This is especially true if you pack Pokemon like Moltres, Volcarona and Talonflame in your team. Why on earth would you use them without Defog and/or Rapid Spin? Seems kinda silly, right? It's really hard to assume that the opponent will always have SR up all the time.
Let's consider the final point of this post, now. That Mega Lucario will always have SD or NP in every situation. Almost everyone thinks it's the easiest thing to set up in the world, even for a fragile sweeper like Lucario! This is far from the truth. I'll credit Kairyu_Gen1 for expanding on my analysis of how hard it is for Lucario to set up SD/NP:
Rotom-Can WoW physical set, or 2HKO special set. If it uses the wrong move though, it'll either get set up on and 2HKO'd by CC or get set up on and 3HKO'd by Aura Sphere
Aegislash-This one mostly depends on prediction. Whoever wins the mind games wins the fight
Talonflame-OHKO's with flare blitz and almost OHKO's with BB. Luke's either switching out or dead
Genesect-OHKO's with flamethrower and blaze kick. Also outspeeds 1st turn and every turn with a scarf
Greninja-Has a 68% (really 54% factoring the miss) chance to OHKO with Hydro Pump, but is always 2HKO'd by vacuum wave. Greninja will either win or cripple most of the time though, and Luke can never set up
Charizard-is outsped and OHKO'd on the 1st turn. Luke can't OHKO without boosts even if it does outspeed anyway
Lucario-Do I need to say it?
Heatran-OHKO each other, but Luke is faster
Gliscor-Physical set's toast unless it has ice punch, but the special set can 2HKO with flash cannon, but will be left with about 10%. I'd just switch out, but if you're ok with a +2 Mega Luke at 10%, then feel free to stay in
Garchomp-Always run from the EQ
Azumarill-without thunderpunch, either OHKO'd by superpower, or 2HKO'd by STABs. Special set can 2HKO Flash Cannon, but it won't work on either AV, lefties, or Sitrus sets
Scizor-Finally a safe one. Scizor's best option is to U-Turn out, dealing very little damage. You'll get very safe set up
Ferrothorn-Easy set up and OHKO. You'll probably get a leech seed and maybe some recoil damage though. Careful about Twave too
Tyranitar-Blue, unless it has Fire Blast or Earthquake, I'd just KO to be safe
Conkeldurr-Get out, it'll just kill you
Excadrill-You both OHKO, but Luke's faster
Dragonite-2HKO'd by coverage moves
Venusaur-Kinda messy theoretically. You can be 2HKO'd by HP Fire, or 3-4HKO'd by Giga Drain, or seeded, or put to sleep. If it has HP fire or sleep powder, you want to run. If it doesn't, you can set up 2 boosts and OHKO with either CC or Flash Cannon
Mandibuzz-special sets can set up and KO, taking ~66% damage in the process, but physical sets will get stalled out or KO'd by foul play
Gengar-You OHKO each other, but Gengar's faster at first
Espeon-If you have a dark move, you should have no trouble. It can set up screens, but it has to guess which one to do since it'll only have 1 guaranteed turn
Mamoswine-You OHKO each other, and Luke's faster, but watch out for sash
Goodra-Physical sets can OHKO (93% chance) with CC, but you'll be left with -1 Def, SpD, and possibly Spe. Goodra always OHKO's with fire blast anyway
Alakazam-OHKO each other, but Alakazam's faster
Landorus-T-Run from the EQ
Togekiss-If you have a steel STAB (other than bullet punch), you're good. If not, you'll probably get Twaved
Skarmory-Luke can boost, then OHKO (only 88% chance on CC), but it risks the whirlwind or taking 50% from BB
Breloom-OHKO each other, but Mach Punch goes first
Infernape-Run, you'll be outsped and OHKO'd
Volcarona-OHKO'd by fire STABs
Kairyu's analysis here demonstrates how difficult it is for Lucario to get a boost. For the vast majority of this list, Mega Lucario has no business setting up at all either because he's so fragile, or he's vulnerable to status, or he has so many weaknesses, or both. Even for the Pokemon who he can OHKO, like Tyranitar, Heatran and Excadrill, they can prevent him from setting up! In fact, out of this list, there are only 3 Pokemon it can set up for sure on: Espeon, Scizor and Ferrothorn, since Skarmory can just Whirlwind him away. The main thing to learn from Kairyu's analysis is that it actually is really hard for Mega Lucario to set up, and there's no reason to assume it will always have SD or NP up.
I'll sum up some of what this overly long post is trying to say for the more lazy people:
1. The main reason Mega Lucario should be considered uber is due to its unpredictability
2. But unpredictable and uncounterable Pokemon are not necessarily uber. See Charizard.
3. There are a couple mistaken assumptions the Mega Lucario for uber proponents make:
3a. SR will always be up. This is false; SR grants the opponent from 1 to 3 free turns to do other things and as a result you lose momentum. Also, Defog and Rapid Spin are a lot more common this generation.
3b. Mega Lucario will always be able to use SD or NP easily. This is exaggerated and false.
What I've been trying to convince the reader is that this argument is not one-sided at all, and I hope this at least partially convinces you that the discussion on Mega Lucario's going to uber is more controversial than it is thought to be. He doesn't necessarily fit the offense or support characteristic because he has many counters depending on a given set. Mega Lucario is a great Pokemon, but not so great that he should automatically be considered uber materal.