Garen vs Malzahar

Trade with Decisive Strike (Q), then Judgment (E), and back off: the Decisive Strike silence stops your opponent from answering with spells.

During Judgment (E), stay closer to your opponent than to their minions: the nearest enemy takes extra damage.

After a trade, back off until Perseverance (passive) kicks in: without recent damage taken, you regenerate part of your health every second.

Activate Courage (W) just before the bulk of the damage: you first gain a shield and tenacity, then a longer damage reduction.

Save Demacian Justice (R) to finish: its true damage grows with the target's missing health.

Get out of the Call of the Void (Q) zone quickly: its two portals fire after a short delay, and their projectiles silence you.

If you have CC, hit him first with a cheap attack, then wait a moment: Void Shift (passive) still ignores CC right after the first damage.

Stay away from minions hit by Malefic Visions (E): if they die, the visions jump to the nearest enemy, and his Voidlings follow them.

Take your trades before he hits level 6: after that, Nether Grasp (R) can lock you down from range while his team hits you.

When he casts Nether Grasp (R) on an ally, focus him: he channels in place, and any CC interrupts him and frees your ally.