Mordekaiser vs Yasuo

Aim Obliterate (Q) at a lone enemy: if only one enemy is hit, the damage increases.

Hit champions or monsters three times, then stay close: Darkness Rise (passive) then surrounds you with a damage aura and gives you move speed.

Pull your targets into the Obliterate (Q) zone with Death's Grasp (E): each spell that hits also counts toward Darkness Rise (passive).

Cast Indestructible (W) when you're taking damage: it turns stored damage into a shield, and a recast converts part of it into health.

Cast Realm of Death (R) on their carry, or their jungler near an objective: you isolate them with you, steal part of their stats, and keep them if you kill them.

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.