When you KOed a Legendary Pokemon at level 42 with one move.
It was only a type advantage.
And a difference of 7 levels. (mine is 49)
tho luckily i saved the game right before i battled cobalion so i just started again XD
my face when i watched the poor thing's health flew from full to zero. ಠ▃ಠ
oh lol, I used like, fifteen ultra balls xD