Samurai guy
Well, here are some suggested changes to keep his theme while doing away with the aspects that make it so frustrating to play against him that he's banned in over half of all games since they implemented the 10-ban system (probably much higher if we were to count double-bans).
Passive: Yasuo gains 100% critical strike chance. The damage amplification of Yasuo's critical strikes is equal to the amount of critical strike chance he has from runes and items. (-10% and 25% damage penalties removed to compensate, since this would apply a -25% to both autos and Q unless more critical strike chance is purchased.) Flow shield removed and base HP adjusted to compensate.
Q: Unchanged
W: Yasuo surrounds himself with a windshield that negates incoming projectiles for the next .75 - 1.25 seconds-- current live duration for the wind wall is 3.75s. The windshield will only block targeted projectiles that are targeted at him (except Caitlin's R). Skillshots that hit him will be negated.
E: Yasuo dashes a fixed distance through target enemy unit. This ability holds up to 2 charges and recharges every 12-8 seconds. If Q is cast while dashing, it acts the same as it currently does.
R: Yasuo blinks to an airborn target, immediately bringing them and nearby allies to the ground and applying damage. Last Breath can critically strike, up to 50% based on the amount of critical strike chance purchased past 50%.
Problems solved with these suggestions, and explanation for how he'll be compensated: Passive: He would no longer get a huge power spike from one and a half items. However, he'll be rewarded with more damage if he decides to purchase more crit items than defense, but of course take a large hit in damage if he opts for more defensive items. And he won't have a shield that resets on cast of his ultimate.
W: He would no longer be able to block a 30,000-50,000 area, and true to his lore will only protect himself. But he'll still retain the essence of the ability.
E: Yasuo would no longer be able to dash through your entire minion wave to get to you, and if he used it to run backwards he won't as often be able to turn around again to gapclose with it. As compensation, he'd be able to double-dash onto a single target if he sits on 2 charges.
R: Rather than keep enemies airborn for an additional second, Yasuo would end an airborn effect if he casts his R as soon as he sees the indicator. And true to the live functionality, he'd deal his damage all at once. (nice joke by riot to have the new skin actually do only one attack to match the fact it doesn't really do three). As compensation for the loss of CC, and to coincide with the passive change, the ability will be able to critically strike but only if he'd have more than 50% crit without his passive.
To explain the Q and R, if he buys ER and PD, he'll still have 100% critical strike chance but his crits will only deal 50% extra damage. For the R, it won't crit with those items alone. If he were then to buy an additional Zeal item, its damage would be increased to 130% (not effected by IE).
Edit: Reposted because some people just see Yasuo in the title and click downvote without reading.