Volibear vs Mordekaiser

Cast Thundering Smash (Q) to charge at your target: your speed doubles when heading toward a champion, and your next auto stuns them.

Hit the same target twice with Frenzied Maul (W): the second hit, on the marked target, hits harder and heals you based on your missing health.

Cast Sky Splitter (E) where you're fighting and stay in the zone: when the lightning strikes, you gain a shield, and enemies hit are slowed.

To dive under a tower, cast Stormbringer (R) near it: on landing, you disable it for a few seconds, and you gain bonus health.

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.