there's also the case of slippery slope: first it's gengarite/mega gengar, next up would probably be shadow tag. But what happens after that? Xerneas maybe? it's very easy to use the terms "over centralizing" and "uncompetitive", both of which i think are bullshit, on xerneas as well.
We made it clear in the original post that this is not, and never, going to happen. Slippery slope is a logical fallacy anyway.
Do not use this as an argument.
Secondly, I want to just get this out of the way because I'm tired of people throwing this around like some sort of holy grail:
Pursuit is NOT a reliable solution to Mega Gengar
Let's start with a basic Gengar set:
Gengar @ Gengarite
Ability: Levitate
EVs: 4 Def / 252 SpA / 252 Spe
Timid Nature
- Shadow Ball
- Focus Blast
- Taunt
- Destiny Bond
The only difference between this set and the standard is the choice of STAB move. You can still trap Grassceus and Fairies without Sludge Wave and Shadow Ball lets you trap Lugia better (who is a very important mon on most stall because it checks like everything), hit Ghosts, and screw Landorus/Gliscor/insert Ground-type here. It is a perfectly viable move and is getting more popular with more Aegislash cropping up on stall/defensive builds.
Here is what this Gengar set does to your Pursuit trappers:
252 SpA Mega Gengar Shadow Ball vs. 252 HP / 4 SpD Mega Scizor: 160-189 (46.5 - 54.9%) -- 62.1% chance to 2HKO (Standard Mega Scizor, Guaranteed after SR)
252 SpA Mega Gengar Shadow Ball vs. 252 HP / 4 SpD Scizor: 192-226 (55.8 - 65.6%) -- guaranteed 2HKO (CB Scizor)
252 SpA Mega Gengar Shadow Ball vs. 252 HP / 216+ SpD Mega Scizor: 118-141 (34.3 - 40.9%) (This 2HKOes with SR + some prior damage or if you come in as normal Scizor)
Mega Gengar also survives CB Scizor BP after Stealth Rock which means it can trap something else immediately after killing your Scizor. There is literally no prediction involved - you just use your STAB move.
Also, Mega Scizor's Pursuit does not KO Gengar if it stays in. Hope you like coinflips!
Now for Aegislash:
252 SpA Mega Gengar Shadow Ball vs. 252 HP / 252+ SpD Aegislash-Shield: 174-206 (53.7 - 63.5%) -- 2HKO
Aegislash cannot OHKO Gengar with either Shadow Sneak or Pursuit, and if it switches out (it is a Ghost so it can if you need it to check Xerneas which is Aegis's actual main job), it failed to trap Gengar. Again, no real prediction, you just click your STAB.
Now for Tyranitar:
252 SpA Mega Gengar Focus Blast vs. 252 HP / 0+ SpD Chople Berry Tyranitar in Sand: 196-232 (48.5 - 57.4%) -- guaranteed 2HKO after Stealth Rock
Tyranitar is more reliable but still risky because unlike Scizor and Aegislash it cannot threaten a weakened Gengar with priority. Also Pursuit doesn't come close to KOing Gengar if it decides to stay in:
4 Atk Tyranitar Pursuit vs. 4 HP / 0 Def Mega Gengar: 134-162 (51.1 - 61.8%)
So yeah, this is also a bunch of coinflips. If Gengar calls your switch and Focus Blasts TTar loses. If Gengar stays in and TTar uses Pursuit TTar loses. If Gengar switches and TTar uses Crunch/Payback, TTar still loses because now Gengar gets to trap something else and it can still potentially Focus Blast/DBond your hopeless TTar. If TTar doesn't switch in at all to save your cleric/Arceus-Grass, why bother running Pursuit on it?
Now before you start laughing at me because I used damage calculations in a suspect argument, it's only meant to be an introduction to my main point:
whether or not your Pursuit trapper actually works depends almost entirely on Mega Gengar's moveset and winning coinflips. I didn't even mention specific things that Gengar can do to royally screw over certain Pursuit trappers like using Reflect Type (which owns all of them, even Tomb), Will-O-Wisp, Hidden Power Fire for Scizor, or even avoiding Pursuit altogether with Substitute - Gengar can beat every common Pursuiter with one set that functions the exact same way as its standard set just by changing which STAB move it decides to use. In the end, you have to pray the opponent's Gengar isn't using a set that beats your chosen Pursuit trapper...which isn't something you can predict from Team Preview, or can even do anything about if you even have the wrong one.
And yeah, while Mega Gengar is frail, it isn't THAT frail. That means actually Pursuit trapping it comes down to coinflips (do I Pursuit or do I use a stronger attack to go for the OHKO) because, hey, Pursuit is actually weak when the opponent doesn't switch out, so much so that Mega Gengar can actually survive Pursuit from Scizor, TTar, and Aegislash if it stays in and attacks! In addition, most teams that use Gengar aren't going to be completely screwed if it gets Pursuited or DBonds the Pursuiter, because most of them don't rely on Gengar as their
sole (primary sure, but not only) means of eliminating the main obstacle to the opponent' sweeper. On the other hand, if Gengar doesn't get trapped, the team relying on Pursuit to protect their other Pokemon is screwed. And even if Gengar is forced to use Destiny Bond for whatever reason, the team using Pursuit still loses something important - their Pursuiter,
which does important things other than trap Gengar. Scizor checks Xerneas and EKiller and might be a Defogger. TTar sets up Stealth Rock, Sand for Excadrill, and checks other really threatening mons to defensive teams such as Darkrai and Yveltal. Aegislash is a hard Xerneas check and beats some other things like Lucario and Mewtwo X. All of these Pokemon fulfill roles that potentially make them the Pokemon Mega Gengar WANTS to trap instead of the other way around.
So basically, if you want to successfully "beat" Gengar, three things have to happen, none of which involve skill:
1. Gengar is not running a set that beats your chosen Pursuit trapper (this is decided by teambuilder, you pretty much have no way of predicting this)
2. You actually win the 50/50 as to whether Gengar will stay in or switch out (This is not a display of skill because there is no "best play" in a coinflip situation, I can name a BOTW and some SPL matches that were decided by coinflips against Mega Gengar)
3. Your Pursuit trapper is not the Pokemon Gengar is actually trying to kill
tl;dr - You are only deluding yourself if you think Pursuit is a reliable way to stop Mega Gengar.
Disclaimer: I never said Pursuit never works. I am saying it is far from reliable.
Disclaimer 2: I did not talk much about Spiritomb because I do not know what set people use on it. If one of you who does use it can share that info with me, I'd be grateful. I would like to say, however, that "Spiritomb" is not a reason to not ban Gengarite. It is, at least from my understanding, even more specialized/niche than Gastrodon, which is impressive.