Sylas vs Cho'Gath

Weave an auto after each spell: Petricite Burst (passive) turns it into a chain swing around you, with bonus magic damage.

Save Kingslayer (W) to finish or to save yourself when your health drops: its healing grows with your missing health.

To engage, cast Abscond (E), then recast within 3.5 seconds: Abduct (E) pulls you to the first enemy hit and knocks them into the air.

Cast Hijack (R) on the enemy whose ult can turn a teamfight: you keep a copy of it, cast with your own stats.

Keep moving against him: Rupture (Q) strikes an area on the ground, and an enemy standing still takes a knock-up, damage and a slow.

Punish him when he goes for last hits: Carnivore (passive) restores health and mana for each unit he kills, and he lasts a long time in lane if you let him farm.

If you have range, keep your distance: his kit has no dash, only the slows from Rupture (Q) and Vorpal Spikes (E).

Don't stay in melee range at low health when Feast (R) is up: its true damage ignores your resistances, even if you're a tank.