The only reason I ask is because of calcualations on psypoke tools
Magikarp can do a POSSIBLE 8550 damage with flail to a minimal defensive mega mewtwo.
Sunkern can do a possible 15447 damage with solar beam
Happiny with destiny bond metronome
252+ Atk Choice Band Pure Power Happiny Helping Hand Facade vs. 0 HP / 0- Def Mega Mewtwo X on a critical hit: 330-388 (102.4 - 120.4%) -- guaranteed OHKO
If psychical happiny can, even without flower gift, everything can.