>>58336800This basically
>>58336829 I see it and I think it needs some buffs. It doesn't really live up to the whole "strongest Pokemon" thing anymore. And granted that's fair next to like Arceus or the creation trio or something, it's not a god. But it should be a lot stronger than it is now compared to some of the other top dogs.
So for its ability, I've seen a few people talk about giving it Neuroforce to let it make the most of all the coverage moves it gets, and I'd say that works. Alternatively you could go further down that route and give it Protean, it would make sense with Mew's ability to transform, Mewtwo not quite being able to do the same, but being able to change its type. Or you could keep it simple and just give it Psychic Surge so it's immune to Sucker Punch and can just nuke everything.
I'd also buff Psystrike. If it ever was good, it really isn't anymore in the days of Astral Barrage and Glacial Lance. So bump it up to 120 base power, and instead of having it be a slightly stronger Psyshock, make it so that it can do either special or physical damage based on whichever will do more.
As for the Megas, they're mostly fine, their main problem is just that using them means not using something else. In a vacuum they're plenty strong. Insomnia on Mewtwo Y isn't exciting, but it doesn't need anything flashy with those stats, and not being able to be put to sleep is huge. Mewtwo X is a little underwhelming though, so maybe drop Steadfast for Inner Focus? Or Scrappy would work too. Oh and it needs some physical STAB moves. Low Kick is situational, Drain Punch is good but not great, and Zen Headbutt just does not cut it.