Shen vs Master Yi

Place your spirit blade behind your opponent before a trade, then cast Twilight Assault (Q): if it passes through them on the way back, your autos hit much harder.

Start a trade with an ability: Ki Barrier (passive) then gives you a shield, and hitting champions lowers its cooldown.

Cast Shadow Dash (E) through the wave to surprise your opponent: the taunt forces them to come to you, and the spell restores energy if it hits.

In teamfights, keep your spirit blade near your carry: Spirit's Refuge (W) forms where it is and blocks autos against your allies there.

Cast Stand United (R) as soon as an ally is in danger: the shield already maxes out at 60% missing health, and the channel delays your arrival.

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.