Galio vs Yasuo

Engage with Justice Punch (E), release Shield of Durand (W), then place Winds of War (Q) during the taunt: the tornado deals damage based on max health.

Against a magic-damage opponent, don't take free hits before a trade: after a few seconds without taking damage, Shield of Durand (W) gives you a magic shield.

Charge Shield of Durand (W) before releasing it, after a Flash if needed: a longer charge means a longer taunt, more damage and a wider area.

Watch the map and join fights with Hero's Entrance (R): your allies in the area get a magic shield, and your landing knocks enemies into the air.

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.