Tryndamere vs Mordekaiser

Keep your Fury high before a trade: with Battle Fury (passive), it raises your critical strike chance. Spend it with Bloodlust (Q) when you need health.

Cast Mocking Shout (W) before a trade against a physical damage champion: it lowers their attack damage, and slows enemies who turn their back on you.

Count on Spinning Slash (E) to stick to your target or to escape: each critical strike lowers its cooldown, more so on a champion.

Wait until you're close to death to cast Undying Rage (R): you can't die during the effect, and delaying it pushes the enemy to take risks to kill you.

Split push in a distant lane to draw several enemies: Undying Rage (R) helps you hold them off while your team takes an objective.

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.