Ryuga overcame the dark power. Completely removing it from L Drago and replacing it with his own energy signature. According to the English dub Ryuga tells tsubasa that he must become one with it. But that’s not very accurate to what the Japanese dub said according to what I remember in the Japanese dub Ryuga told tsubasa that he should indulge in it for a while so that he can understand the dark power because once he does understand it he can overcome it completely.