ForgetsThis is completely retarded.
If Sidious is the most powerful sith lord of all time, then Caedus, being a sith lord, is obviously weaker. So Yoda wins.
a) Sidious is noted to be the most powerful Sith Lord in history as of The Phantom Menace. Then as of Revenge of the Sith. Then as of Death Star. Then as of Dark Empire. You'll note how none of those extend to Legacy of the Force.
b) Being "the most powerful" =/= being the greatest combatant.
c) Your ABC arguments sucks.