Kill: Sylvanas, not because I hate the character - I actually think she's pretty alright and one of the better-written Warcraft characters - but I think it would be a huge turning point in the story and it would be interesting to see how the Forsaken coped, and who their new leader would be.
Resurrect: Kel'thuzad
Redeem: Jaina, as everyone else has said. I want to see the character go back to being likable again. I'm sick of this emotional rollercoaster treatment she keeps getting in out-of-book lore.