Irelia vs Master Yi

Mark your targets with Flawless Duet (E) or Vanguard's Edge (R) before Bladesurge (Q): if the target is Unsteady or dies to it, its cooldown resets.

Before a trade, hit minions with Bladesurge (Q) to stack Ionian Fervor (passive): each stack gives attack speed, and at max stacks your autos hit harder.

Place the two blades of Flawless Duet (E) on either side of your target: only enemies caught between them are stunned.

Use Defiant Dance (W) to absorb a burst: you take less damage while charging, and the longer you hold it, the harder the release hits.

Against Highlander (R), don't run alone: regroup with your team, because he gains speed and ignores slows.

If you have CC other than a slow, land it right after Alpha Strike (Q): during the strike, he's untargetable, and Highlander (R) ignores slows.

If you have CC, interrupt Meditate (W): he channels it to heal, more at low health, and to reduce the damage he takes.

Put pressure on his jungle early on: Master Yi is strongest once he has his items, and each stolen camp delays him.