Okay, I only wanted to post 1 comment on this thread, but this is getting ridiculous now. You cannot use an argument about the megas that we do not have yet being able to balance out the metagame. Are we supposed to wait for months until the right mega stones are released to balance out the tier with respect to Mega Metagross? Of course not! We need to try and make the metagame as fair and balanced as possible at all times regardless of whether or not something has been released yet. Please try to make arguments that actually are relevant to what the current OU metagame actually is at present.
If you want a good counter argument, here:
Mega Metagross is a very powerful pokemon that is a powerful force to behold in the OU tier. It has very solid stats, it sits at a very solid speed tier of base 110, and it has a very wide array of moves at its disposal. Mega Metagross is very difficult to deal with due to its strong offensive presence and versatility; however, Mega Metagross suffers from a lack of recovery, must be built carefully to match the team it is placed on, can be whittled down easily throughout a battle, and finds difficulty switching directly into battle due to its overall value on any team. Mega Metagross does not have 4 moveslot syndrome since it is able to potentially perform its role as a powerful wall breaker regardless of the moves it opts to run (no matter what, it will be hitting something for some damage essentially). Although Mega Metagross does not "technically" have 4 moveslot syndrome it does have a common trait across all of its most common and viable sets: There is always a way to beat it regardless of whatever 4 moves it runs. It always has Meteor Mash, that's not really arguable. So then you have 3 moves which can consist of: Zen Headbutt, Earthquake, Hammer Arm, Ice Punch, Thunder Punch, Grass Knot (for Hippo, Slowbro, Gastrodon, Quagsire, and several others which may appear from time to time; of course this is the least likely coverage move it will run), HP Fire, or Bullet Punch (yes Agility/Rock Polish are technically valid, but are rarely seen). So how are you supposed to go about handling Metagross-Mega when it has such an unpredictable array of moves available? As I stated earlier, there is always a way to beat Mega Metagross no matter what it wants to run. Many people have repeatedly stated that you have to switch in and out of battle just to scout for its moves to figure out its counters and valid checks. This is simply not always true. There is more than one way to skin a cat as the saying goes. As I stated what Mega Metagross' faults were, all of them can be taken advantage of in several manners (lack of recovery, must be built to match its team, easily worn down throughout a battle, difficulty directly switching into battle due to the need to preserve its longevity).
Metagross, like any offensive pokemon, can be pressured not to come out into battle at all. With enough offensive pressure, a player is able to keep certain pokemon from coming into battle. Since Metagross lacks recovery and very rarely wants to directly switch into attacks to maximize its longevity, it can potentially find some difficulty entering the battle against strong offensive pressure.
http://replay.pokemonshowdown.com/gen7oususpecttest-553431857 Notice how my opponent did not want to send Mega Meta into the battle. The pure pressure being put on from Kingdra in the rain and the possible defensive answers in Gastrodon and M-Scizor kept Mega Meta out of the battle until it was too late for Mega Meta to really do much of anything. I've noticed through playing enough competitive pokemon that most offensive spam teams/cores have a tendency to cause this type of offensive pressure which scare something from entering the battle to an extent. So this is only a minor instance of how one might take advantage of Mega Metagross' faults since it is limited to a certain type of offensive build.
Okay, so what about when it CAN come into battle because you might not have the right type of offense for that purpose? That brings us to how it can be punished via defensive pressure if it chooses to enter the battle or how it can be quickly worn down through offensive counterplay.
http://replay.pokemonshowdown.com/gen7oususpecttest-533238829
http://replay.pokemonshowdown.com/gen7oususpecttest-533228976
http://replay.pokemonshowdown.com/gen7oususpecttest-533172512
http://replay.pokemonshowdown.com/gen7oususpecttest-533132265
http://replay.pokemonshowdown.com/gen7oususpecttest-554386188
http://replay.pokemonshowdown.com/gen7ou-539439379
Alright, so there are several replays there depicting how you can both defensively and offensively handle Mega Metagross. Though the terrains may benefit Mega Metagross, they can also benefit other mons to a much greater extent in some cases, such as Heatran in grassy terrain. Kartana can set up on Metagross without hammer arm if they run the SD timid set to get a speed boost from their ability (controversial as a set or not, you can't deny it's a set that exists). Rocky Helmet Tangrowth and AV Tangrowth can counter/check and check Mega Meta respectively. Physically defensive Zapdos is another really good answer to Mega Metagross on defense and on offense and quickly wears down Mega Metagross. There are a ton of potential answers that will vary depending on Metagross' set; however there is no argument that Mega Metagross will always run coverage for all those answers at one time. It simply can't. I understand the metagame has changed since some of those battles happened, but that has nothing to do with Mega Metagross seeing as it hasn't actually changed within the OU meta due to it running the same role as a hole puncher on essentially every team. So when you get into the idea thinking you have to pivot around to figure out its moveset, you should also think of the idea that Mega Meta doesn't blatantly OHKO everything in its path and that there are some things which you could leave in battle against Mega Meta and immediately begin to wear it down whilst learning its moveset in the process. Stall playstyles can't really do that, but stall does have Dugtrio, Skarmory, and other evil stall monsters that appear which can be a headache for Mega Metagross.
As several people have already stated, Mega Metagross is probably not going to stay in battle for more than a couple of turns before it leaves, which in turn means it will (probably) have to take hazard damage again at some point and is likely going to have to wait until it can be brought into battle safely.
I'm not going to repeat my argument that I made earlier in this thread explaining why I am leaning towards a ban. Just know that I am leaning towards a ban solely due to the fact that I think it over-centralises the metagame a little too much. If you're curious, go to the page where I make my argument.
Anyway, please make your arguments and counter-arguments on sound reasoning that has to do with the metagame that exists with respect to Mega Metagross. Don't bring things that don't exist into the equation. We're looking at Mega Metagross in its own entirety.
Do Not Ban.
(edit: I changed my mind having tried laddering on 3 different accounts. The OU metagame without metagross is just... frustrating to say the least)