Oh, believe me, I have ideas for powerful enemies in mind, which isn't even getting into what the Leader can do if she must.

But, well, in terms of overpowered....

Basically the character I want to use but absolutely cannot use in any RP ever can kill _anything_. Absolutely anything. Immortality doesn't save you, she can kill immortal beings, phones, people, concepts, magic, illusions, deities, walls, potential futures, explosions, psychic powers, diseases... The list goes on.