Sion vs Urgot

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.

Don't move around him during a trade: Echoing Flames (passive) fires from the leg facing his target, and each leg has its own cooldown.

Take a trade when Disdain (E) is on cooldown: it's his only dash, the one that stuns the first champion hit and throws them behind him.

If Fear Beyond Death (R) impales you, back off and stay above 25% of your max health until the effect ends: below that, he can drag you in and execute you.

Back off when he activates Purge (W): he deals and absorbs a lot with his chain gun, but moves slower during the effect.