Except... one major problem. How many teams run more than one of those Pokemon? Its not like these are obscure niche counters to those Pokemon. They are some of the most common Pokemon in the game, and the vast majority of them will do enough to Gengar to prevent it from trap killing anyone else, even if they do go down. So, woo, you found a counter to a pokemon your team is weak to. Big deal. Carrying things to beat Pokemon the rest of the team was weak to is how team building works. So it fits on competent teams. That's wonderful.
Also how many of those is it actually guaranteed to beat anyways? In the first example case: Skarm has sturdy and can phaze or just take a massive chunk out with Brave Bird. Gyara can DD when Gengar switches in (which is has to do to trap, unless it is waiting for a KO, in which case it likely already has DDd anyways) and procede to KO. Dragonite can do the same and also has Multiscale. Gliscor and Lando both have EQ, so Gengar can't switch in unless it is not Mega yet, in which case it can't trap. Slowbro and Celebi might lose most of the time, but Gengar can't freely switch in on either.
Now, I'm not saying that Gengar can't beat those guys. What I am saying is that you talk like simply having a Gengar with that set makes those Pokemon irrelevant while in reality it can't necessarily reliably trap anyone of those without first sacrificing a teammate, and when the argument revolves around how it is removing important Pokemon, forcing yourself to sac something may be doing just the same for the opponent, which defeats the entire purpose. Sure, with good prediction and/or the right support you can do it without losing something, but, with good prediction and/or the right support everyone can beat everything, so that is frankly irrelevant.
Gengar is an awesome Pokemon that can beat a ton of other stuff, but its not a catch-all kill button for whatever you want to counter. Its good and definitely deserves a suspect test, but what it does is not so far ahead of all the other best Pokemon in the tier that it should be quick-banned. It deserves a fair test where People will actually work to find the best counters and stuff and not talk out of blind faith in one side or the other.
Firstly, if you are running (say), both Gliscor and Landorus-T on your team, then you are handicapping your team, period. The average player generally doesn't have the teamslots to spam his teams with walls that only counter the same amount of pokemon - its just not productive. Secondly even if you did run into a team that has 2 counters to your one sweeper, thats fine, decide to focus on a Azumarill sweep or whatever instead. There has not been a single OU battle that I have played, where I have not sized up my opponents team, and then actively looked for weaknesses, walls or offensive mons that need to take a little bit of prior damage etc for x to sweep. It won't always be my star sweeper that wins, occasionally they will hyper prepare for your main sweeper, leaving themselves weak to something else on my team that I can exploit. Mega Gengar just makes exploiting this so much easier, since you can trap and eliminate such a wide variety of pokemon with its customised moveset, letting it support multiple sweepers at once with very little counterplay.
Secondly I can expect it to beat most of those. Skarmory might have study (assuming SR isn't up), but thats ok, its on 1%, whatever it dragged in prolly beats it now, and guess what YOUR SKARMORY NO LONGER WALLS MY LUCARIO. Sure, ok, maybe for whatever reason I didn't steal a 100% ko, but I did my job, I crippled your wall (assuming whatever switches in doesn't just KO 6-7% Skarm after leftovers), and Lucario now has one thing to worry about.
I am potentially assuming the Gyarados set most frustrating to Lucario would be Rest Talk, but whatever, Gengar can still get safe switches off slow U-Turns, or well timed double switches. IIRC Mega Gengar might even outrun Gyarados at +1 (don't quote me, I might very likely be wrong). Dragonite might be in a similar boat, and STILL doesn't exactly get a free set up due to again, the possibility of a slow U-Turn (and ignoring SR as a hazard). Even if, by some miracle, your Dragonite survives my powerful hit, and Gengar goes down (remember I always have Destiny Bond as an option so long as I am faster), I prolly weakened you enough for Lucario to sweep anyway. Like Jas, your missing the point, its not really at all difficult for Mega Gengar to come invia slow pivots / double switches, and you can get its only going to come in when its sure it can pull off the trap kill 100% of the time. Its sure as HELL not switching into Earthquakes, so im not understanding what your on about there, and its even acceptable for me to sac something, bring in Gengar, trap your wall stopping my Lucario, Destiny Bond and take something else down with me, and then use my Lucario to clean sweep now that your counter / check has been eliminated. Not to mention that in many cases, your stuck attacking off the bat. What are you do assuming you get Celebi / Slowbro in, spam Psychic all of the time (NO TIME TO HEAL MUST HIT GENGAR) and hope you hit my switch. Assuming obviously, that I don't just bring in a psychic resist instead.
I don't like applying the right prediction ---> everything needs prediction ---> nothing is broken argument either in these case, especially since Gengar puts you under so much more pressure, than the Gengar user is under. Its called Risk vs Reward, and with Shadow Tag Mega Gengar has very little counterplay, thus allowing it to pull off its trap kill much easier than other pokemon can claim.
Gengar is an awesome Pokemon that can beat a ton of other stuff, but its not a catch-all kill button for whatever you want to counter.
This is exactly what Gengar is, you have seen me use Gothitelle against you during the very recent CAP playtest (albeit a shitty, gimmicky Gothitelle set), you know how it works, Mega Gengar is so much more better than Gothitelle at what it can achieve, and as a player, its legitimately very frightening when playing against a quality player with Mega Gengar, since its so tricky keeping your key mons alive due to the limited about of counterplay Shadow Tag gives you.
