Locke vs Master Yi

Cast Ritual Nails (Q) before Ashen Pursuit (E): your hits consume the nails stuck in the target, and each extra nail adds damage.

Finish off wounded targets with autos: Silver Stake (passive) adds magic damage that grows with their missing health.

Activate Soul Ignition (W) at the start of a trade: it costs you health, but at the end, you heal back part of the last damage taken, plus more based on your missing health.

Save Ashen Pursuit (E) for a sure kill or to escape a gank: it's your only instant movement, it has a 10-second cooldown, and only a takedown resets it.

Save Purgatory (R) to finish: it seals marked enemies below a health threshold, and when you pick up the artifact, each sealed champion raises that threshold for good.

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.