Camille vs Master Yi

Wait a moment before the second Precision Protocol (Q) attack: after a short delay, it hits harder and part of its damage becomes true damage.

Hit your opponent with the outer half of Tactical Sweep (W): they are slowed, take extra damage, and you heal for part of it.

Fire Hookshot (E) at a wall near your target, then leap: you stun champions where you land, and the leap goes twice as far toward a champion.

Cast The Hextech Ultimatum (R) on their carry: they can't leave the zone, other nearby enemies are knocked away, and you interrupt their channels.

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.