Master Yi vs Nasus

Cast Alpha Strike (Q) to dodge a spell or a burst: you're untargetable during the strike, and your autos lower its cooldown.

Cast Meditate (W) to tank a burst mid-teamfight: you take less damage, heal more at low health, and the time left on Highlander (R) is paused.

Activate Highlander (R) to chase: you gain move speed and attack speed, and slows no longer affect you.

Chain kills in teamfights: each takedown lowers the remaining cooldown of your basic spells, and extends Highlander (R) if it's active.

Early on, take a trade whenever he steps up to last-hit a minion: each kill with Siphoning Strike (Q) increases its damage for the whole game.

Freeze the wave near your tower: to farm with Siphoning Strike (Q), he then has to step up and expose himself to ganks.

Once he hits level 6, don't engage during Fury of the Sands (R): for 15 seconds, he gains health and resistances, and his area damage scales with your max health.

In teamfights, if you're ranged, hit him while backing off: he has no dash, only Wither (W), a slow that grows stronger over time.