Nocturne vs Master Yi

Fight on the Dusk Trail left by Duskbringer (Q): on it, you gain move speed and AD, and you move through units.

Stay near your target after Unspeakable Horror (E): if the tether holds until the end, they're feared, and you gain move speed toward them.

Cast Shroud of Darkness (W) just before their CC: the barrier blocks the next enemy ability for 1.5 seconds, and a successful block doubles the spell's attack speed bonus.

Cast Paranoia (R) when an enemy is isolated: they can no longer see their allies, and you can launch yourself at them from long range, farther with each rank.

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.