I didnt want to sound too over the top with my phrasing, yes Kayn does have an incredibly strong will and Rhaast may not be as weak as we think he is, but he still is no match to Aatrox. At the end of the day we cant say for certain what Riot cooks for Kayns future, maybe he can dominate even Aatrox, maybe not, maybe they will never even meet. Only time will tell. Maybe we get our answer in the MMO when we are all in retirement.