Blissey is only happy because she knows nearly nothing can hurt her. Want to know why? Wait till you see the size of her health bar. As the final evolution of Happiny, Blissey starts at around 255 ...

This ranked list classifies the worst Pokemon Mega Evolutions according to stats, competitive value, and overall potential.

though it does get a bit complicated when you have to adjust for the various regional evolutions. Pokemon Base Stage 1 Evolution Stage 2 Evolution Bulbasaur ...