And we are talking a Pokemon with more overall bulk (~8% better physically, ~5% worse specially) than Eviolite Chansey if running its common specially defensive spread. And with actually nice offensive stats, a really solid boosting move and the best STAB a physical Ground-type Pokemon could ever wish to have.To think, just two weeks ago, no sane person would have made this claim.
Pokemon is weird, man.
(Zen Headbutt modified as to have the same BP as Psychic)
0 Atk Mew Zen Headbutt vs. 4 HP / 252 Def Eviolite Chansey: 141-166 (21.9 - 25.8%) -- 2.6% chance to 4HKO
0 Atk Mew Zen Headbutt vs. 252 HP / 4 Def Zygarde: 82-97 (12.8 - 15.2%) -- possible 7HKO
0 SpA Mew Psychic vs. 4 HP / 252+ SpD Eviolite Chansey: 46-55 (7.1 - 8.5%) -- possibly the worst move ever
0 SpA Mew Psychic vs. 252 HP / 252+ SpD Zygarde: 73-87 (11.4 - 13.6%) -- possible 8HKO
How we underestimated something with that bulk is anyone's guess.