Kai'Sa vs Yasuo

Cast Icathian Rain (Q) on an isolated target: the missiles split between nearby enemies, so a lone target takes them all.

Attack right after your support lands CC: with Second Skin (passive), your allies' immobilizing effects also stack Plasma.

Before Killer Instinct (R), stack Plasma on your target, from range with Void Seeker (W): the dash needs a marked target and gives you a shield.

Make use of each spell that Second Skin (passive) evolves: Supercharge (E) makes you invisible to get in, and Icathian Rain (Q) fires more missiles at a lone target.

Hit him with a cheap attack to trigger the Way of the Wanderer (passive) shield, then start the real trade: otherwise, it absorbs your best damage.

If you have projectiles, save them for after Wind Wall (W): it blocks them all for 4 seconds, on a 25 to 17 second cooldown. Other spells go through it.

Don't stand right behind your minions: each one gives him a target for Sweeping Blade (E), and he gets closer to you with every dash.

Get out of the line of his whirlwind, the third Steel Tempest (Q): without a knock-up, he can't cast Last Breath (R).

Judge his threat by his crit items more than his level: Way of the Wanderer (passive) raises his critical strike chance, so each crit item does more for him.