>>54867861Probably Necrozma? The thing destroyed it's home dimension, I think.
Stuff like Eternatus and the Original Dragon could be on par, but we really don't see or hear of them really doing anything. Just vague stories about them being "super strong, trust me bro"
Rayquaza is the one with the most concrete data on, destroying an ecosystem collapsing meteor, but I think I'd give it to Necrozma