
Count Nefaria is a pretty powerful opponent to the point where he was able to easily best the Avengers. He has also gotten the better of Thor on occasion. At their peaks though I would take Thor to defeat Nefaria. Thor has more stamina and is able to maintain his power level for greater periods of time than Nefaria. Ultimately Nefaria is able to boost his power level to around Thor’s level but he has less experience using these abilities. Thor wins.