Originally posted by Haschwalth
Sure, because Darth Sion is totally stronger than Malgus/Arcann/Vaylin/Bane, yeah you get the point.
And you don't, apprently. I didn't say willpower was the only source of Force power, but it can be used to achieve the same results as those with more talent or knowledge. In the case of Sion, it allowed him to attain immortality without the need for extensive study or a deep grasp of the Force.
Several characters in-universe have come to this same realization, Darths Plagueis and Wyyrlok himself being examples. Wyyrlok believed a Sith's strength derived from willpower, and his theory actually showed results.
With his sheer force of will, Wyyrlok was able to circumvent the knowledge and mastery required to understand Andeddu's technique, so despite never having heard of it, he was able to instantaneously utilize it and actually reverse it back on Andeddu with greater potency.
Of course willpower isn't the only variable in determining an individual's Force strength, as raw talent and knowledge also play a key factor, but willpower is still very significant nonetheless. And it's not that Wyyrlok lacks in the Force knowledge department, being the One Sith's loremaster and an expert on Sith Alchemy and Sorcery. That, plus his own feats and scaling is what makes me confident in his ability to win a wizarding duel against Bane.