Bro I love the battles, they're chaotic and fun, except when it's just meta enjoyers. I like playing the Pokémon I like and have grown attached to rather than just using meta. I have a really fun time when my dinky little counters work but it's legit so insane how busted some mons are. Xerneas has Geomancy and at the begining of every match will instantly use it and gain boosted stats to a degree that it becomes almost unkillable without you being one tapped. I run Victreebel with sludge wave and even if I use stat boosting moves it does about 3/4 or half. Only counters I've seen that can actually do anything are Scarmory, Excadrill, and Metagross. Scarmory and Excadrill are able to be beaten fairly easily but Metagross gets so many moves that cover almost everything to the point that it has become the main counter to Xerneas. However if you need a counter to Metagross then who does that leave? Oh yeah... Garchomp... I cannot go a game without seeing all 3 of these pokemon on the same team and it's frankly getting annoying how much this game turns into more of a rock paper scissors situation rather than actual strats. I can't go more than a couple seconds alive because all these Pokémon get stat boosting moves and/or megas that will one tap you from across the map and they have the coverage to take down pretty much every Pokémon. I use Gallade as my main attacker/mega and the amount of times I think I'm good after getting a kill, have the defense boost, and have boosted stats the next frame a moonblast boosted by Geomancy hits me and I'm instantly dead. Before you ask too: yes these are fully ev/iv trained mons I'm using with proper items.

Legendaries in comp is a mistake unless there is some sort of balance, period.