Im not super well versed in canon, expanded universe stuff but, besides the obi wan series finale, i cant think of another moment of someone legitimately defeating vader in a fair fight after he fully became vader after mustafar. If someone does beat him they always seem to use some tricks or something to disable or distract him before slipping away.

With obi wan in ANH vader wins. With luke at bespin vader wins despite clearly holding back. With luke on the 2nd death star it seems like vader was still holding back based on luke saying he sense the conflict in him which seems to be how luke beats him, at least in part.

Aside from starkiller (who is legends now anyways) i cant think of anyone who has legitmately outmatched vader in a fight. Is there anyone?