Vader. Khan had surprise and a vastly superior weapon. Vader walked into the sort of entrenched position that would almost qualify as an ambush and still dominated.
Vader only had opponents in front of him and he used his powers and abilities against what kinds of troops ? Were those guys elite troops ?
Prior to Uhura exiting the spaceship she said they had no chance of winning against the Klingons with their numbers and firepower if they came out blazing. Kirk was in awe of Khan's decimation of the Klingons and he wasn't working alongside the Enterprise crew at that point.
Khan also took out multiple Klingon ships as well as more Klingons than Vader took out. Khan wasn't in a position that his foes were all in front of him.
I guess you believe those rebels were greater than the Klingons and the ships Khan wrecked. Is that your position ?