The only unique ones seem to be Xicor and Dark Goku. Victor could be an immortal type character causing serious trouble for the Z fighters if he's irredeemable. Redeemable villains tend to be trash and fake villains.
Dark Goku isn't all that, he would end up getting flattened since he would be around Goku's level. The only way he would be worth it is if rage and malevolence fuel a saiyans power beyond it's normal capacity. That way he would always be leagues above the Z fighters.