Witchcraft

Would anyone mind giving me some good ideas for a dark-magic demonic superhero, I've been having some real trouble working on what kind of powers/skills this kind of character would have, they could be a witch or a sorcerer.

I could take inspiration from users of dark magic, like Raven, Nico Minoru and John Constantine, but I would love to hear other ideas.

Two questions:

What is your ideal magical/mystic ability? Nothing Omni or instant godhood.

&

Whats your favourite magic system or type of magic? Can be from a show or a non-specific form of magical expression

Has anyone ever made a superhero character that uses magic. If so, what was your inspiration for your magic-user.

I'm trying to develop my magic-users so they can be more interesting, I've taken inspiration from other magic-using characters, but it would love to hear some advice from other people more experienced in writing.