Q'Anilia
Exiled Master Jedi
Assuming RPG is included (Which it should be, given it's canon) as well as assuming what I've heard of Ganondorf is true:
Sylvanas: Ganondorf 8/10
Vashj: Ganondorf 10/10
Kel'Thuzad: Kel'Thuzad 9/10
Illidan: Ganondorf: 6/10
Azgalor: Ganondorf: 7/10
Lich King: Lich King 10/10
Ganondorf would one-shot a majority of these characters. I'm basing the outcome on the fact that those that win a majority, or win a few are competent enough fighters to avoid him the period of time required to bring him down.
His telekinesis and soul destruction would be the two most dangerous abilities. Vashj is powerful, but doesn't have enough tricks up her arm to counter the hulking Ganondorf. Azgalor would rely on weakening him to the point where his attacks aren't dangerous.
Kel'Thuzad can freeze time, do nasty things to his soul, dispel telekinesis, wilt his body and much more.
The Lich King, he's just way too much if you put him on RPG level combined with his overall appearances and give him Ganondorf strength.