[Meta thread] Iron's PokeRole Adventure: The Skull Ruins

[Dragonstrike]

Well, one detail the alolan pokedex neglects to mention is if a strong bond with a trainer helps prevent the doom and gloom in most of the entries for the mega evolutions.

In the anime, Korrina's mega Lucario acted like the alolan dex entries described: ruthlessly and uncontrollable.  Once her bond with Lucario was more solidified, though, she could perform the mega evolution with no adverse side effects.

And in Super Mystery Dungeon, all pokemon that Mega Evolve go Berserk if they maintain the effects of Mega Evolution for too long, but can handle it perfectly fine for short periods of time.

So I personally think that having that strong bond with your pokemon is essentially only a requirement for a safe mega evolution with no drawbacks.