Gnar vs Mordekaiser

As Mini Gnar, poke and kite with Boomerang Throw (Q): it slows, and catching it on the way back lowers its cooldown.

As Mini Gnar, land three hits on the same target: Hyper (W) then adds damage based on their max health and gives you move speed.

Engage when your Rage Gene (passive) bar is almost full: your next ability turns you into Mega Gnar, tankier and with new spells.

Cast GNAR! (R) to send enemies into a wall: those who hit it are stunned and take more damage, the others are only knocked back.

Stay near your minions against Obliterate (Q): its damage increases when it hits only one enemy.

Dodge Death's Grasp (E): it pulls you toward him, into his other spells, and it has a 16 to 8 second cooldown.

If you have range, kite him: Mordekaiser has no dash, and only Death's Grasp (E), which pulls you in, closes the distance.

In Realm of Death (R), save your mobility spells to escape him rather than for the duel: he steals part of your stats, and keeps them if he kills you.