Talon vs Master Yi

Apply three Blade's End (passive) stacks by hitting with your spells, then strike with an auto: the target starts bleeding and takes heavy damage over time.

Cast Noxian Diplomacy (Q) in melee range when you can: instead of the leap, it lands a critical strike. If it kills, it heals you and comes back faster.

During Shadow Assault (R), break invisibility with an auto or Noxian Diplomacy (Q): the blades then converge on your target instead of coming back to you.

Push your wave, then roam by vaulting walls with Assassin's Path (E): the spell comes back fast, but you can only cross the same wall again after a long delay.

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.