Sion vs Sett

Last-hit minions and monsters for Soul Furnace (W): each kill permanently gives you max health, more on champions, large minions and large monsters.

Slow your target with Roar of the Slayer (E) before charging Decimating Smash (Q): they're less likely to get out of the area.

Charge Decimating Smash (Q) for at least 1 second: below that, the hit only slows, and beyond it, the knock-up and stun last longer the more you charge.

After you die, hit the nearest champion: during Glory in Death (passive), your autos are much faster, heal you and deal damage based on their max health.

Cast Unstoppable Onslaught (R) from far away to engage or roam: unstoppable for 8 seconds, you stun longer and hit harder after a long charge.

Get out of the center of Haymaker (W): it deals true damage there, and the sides only deal physical damage.

Keep your distance once Knuckle Down (Q) is used: he has no dash, and it's this spell that speeds him toward you.

Don't take a big trade unless you can finish it: Haymaker (W) stores part of the damage he takes as Grit, for a stronger shield and punch.

Don't stay grouped behind your tank: The Show Stopper (R) can slam them onto you, and the damage depends on their bonus health.