Nefretiri
At first, it was nearly impossible to tell the difference in their skill. Neither holding back and not waiting for the offensive. You could see their hatred for each other and how much they wanted to end the other's life. Still, they had to rely only on their combat skills without access to their supernatural abilities, and both had abundant talent. However, the tide quickly changed.
There were so many things they shared. Both had a love of battle, endurance, speed, and strength. I watched them both quickly assess the changes in the fight to see when the other was getting tired, but I saw the problem my 'ex-husband' has that Ivan doesn't. It isn't experience that was giving Ivan the upper hand. Ricky was an assassin, and though that was a different line of work than being a soldier and warfare that Ivan knew and understood, the hand-to-hand experience was necessary. They both knew what it was to survive life-or-death situations.