Bel'Veth vs Master Yi

Chain Void Surge (Q) in different directions: each direction has its own cooldown, which drops with your attack speed.

Cast Above and Below (W) when the target can't dodge it: hitting a champion knocks them into the air and refreshes Void Surge (Q) in that direction.

After a kill or an epic monster, eat the Void Coral with Endless Banquet (R): your true form gives you health, range and attack speed.

Take large monsters, large minions and kills: Death in Lavender (passive) gives you permanent attack speed for each one.

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.