Mega Absol also has fabulous hair.
When this Pokémon whips the winglike fur on its back as though beating its wings, it sends an intimidating aura flying at its opponents.
– Pokémon Sun Pokédex
Absol Mega-evolves into Mega Absol. Its typing doesn’t change, but it gets a much better ability in Magic Bounce (which are only available on Espeon and the Natu family as Dreamworld abilities).
Design-wise, I think it got more elegant and somewhat feminine, with its hair over the eye being longer and having wing-like things added to the collar (would it be able to fly with those wings? Why is it not part Flying?)
Normally Absol has great Attack, but usually is too slow to take advantage of it, having thin defenses and not a great defensive type. Its mega evolution supposedly raises its Attack and Speed (not sure by how much), making it more useful (aside from Magic-bouncing things).