Aphelios vs Swain

With Gravitum as your main weapon, hit your target to slow them, then cast Weapon Abilities (Q): the cannon roots every enemy it has slowed.

Switch to the right weapon with Phase (W) before Moonlight Vigil (R): you then attack each champion hit with your main weapon, and its effect applies.

Before an objective, check Weapon Queue System (E): it shows the weapon Alune will give you next, and an empty weapon goes to the back of the queue.

Get out of the Nevermove (E) path as it comes back: it only roots on its return to Swain, then he can pull each rooted champion to him.

Leave the area as soon as Vision of Empire (W) appears: it strikes and slows 1.5 seconds later, and each champion hit gives him a Soul Fragment.

During Demonic Ascension (R), back off and hit from range if you can: he only drains nearby enemies, and his form ends when he stops draining.

If you have Grievous Wounds, apply it during Demonic Ascension (R): the drain heals him every second, and that healing keeps him alive.