1v1 Kayn vs Yasuo which form?

you would lose in both if both players are of same skill level. You cant out damage, out sustain crit.

Rhaast is just all around much better imo (tried out both a bit during the free week). The only thing Shadow Assassin has that's relevant to a 1v1 w/ another melee champ is slightly more burst. Compare that to Rhaast's % dmg (less relevant against Yasuo because he doesn't usually build too much hp), W hard CC (very relevant), and healing off of damage dealt (very relevant) and it's pretty clear which choice is better.

Red for is much better for dueling since you cant really one shot him with assassin if he gets some defense

Shadow assassin! W (if it lands) then go R( with SA form your ult cast range is big also ur w so its easy to land . Once ur ult activated come out and Q and one AA he is dead. What the hell can he do? He can only watch. People who say SA is weak are people who dont know how to play kayn.