Well, it is described as trainers who use mega evolution only care about winning and not their Pokémon's wellbeing Lucario even loses control of itself when it mega evolves (Most of the time) as shown in XY.
GHOST TYPES ARE DEAD PEOPLE; POKÉMON MAKES STUFF FOR KIDS; MEGA EVOLUTION TORTURES THE POKÉMON; LAVENDER TOWN SYNDROME EXISTS; AN EPISODE OF THE ANIME GOT TAKEN DOWN FOR HOSPITALIZING 700 JAPANESE KIDS; LOOKING UNDER MIMIKYUS CLOTH IS A DEATH SENTENCE; DRIFTLOON KIDNAPS CHILDREN