Under what circumstances would a duel like this have happened, would it have been a formal arrangement or just the two commanders happening to meet on the battlefield? And when one commander won, what did that mean for the battle as a whole?
I would like to point to u/Iphikrates with the Ancient Greeks almost certainly did but stopped doing it as not very effective
I discussed the one time commanders (unless you mean not just head of armies) duelled in the three kingdoms era, Lu Bu vs Guo Si
Fantasy certainly oversells how often these things happened in ancient battles and winning a duel doesn't seem to have had much effect on the wars themselves.