Ekko vs Gragas

Throw Timewinder (Q) at a champion, then position so the device passes through them again on its way back: it expands into a slowing field, and the return hits again.

Hit with Timewinder (Q) out and back, and weave in the empowered auto from Phase Dive (E): the third hit triggers Z-Drive Resonance (passive), with bonus damage and speed.

Cast Parallel Convergence (W) where the fight will happen, then step into the sphere when it appears: you stun the enemies inside and gain a shield.

Engage, deal your damage, then cast Chronobreak (R): you return to where you were 4 seconds earlier, in stasis, and recover health based on what you lost.

Stay behind your minions: Body Slam (E) stops on the first enemy it meets, minions included.

Get out of the Barrel Roll (Q) area right away: the longer the barrel sits on the ground, the more its explosion hurts and slows.

Step up when Body Slam (E) hits nobody: its cooldown isn't reduced and stays at 14 to 12 seconds.

Spread out from your allies: Explosive Cask (R) knocks every enemy away from the impact, which can split you up or send you toward his team.