They did it in the RPG daysYou can argue endlessly, but remember that everything is possible in this fantasy universe.
1) It is possible to kill Mannoroth by mortal orc.
2) It is possible to injure a titan by mortal orc.
4) It is possible to kill the demigod Cenarius by mortal orc.
5) It is possible to kill the Lich King by mortal human.
Etc
Everything depends on the situation.
It's easier to ask the developers to rank ierarchy the power of ALL Warcraft characters than to try to find the answer in a forum about the winner in duels. Even in mortal kombat, Striker can defeat Raiden.