Lucian vs Swain

Weave an auto between each spell: Lightslinger (passive) turns it into a double shot, and each shot that hits lowers the cooldown of Relentless Pursuit (E).

Attack right after an ally's heal or shield, or a nearby enemy getting immobilized: Lightslinger (passive) then empowers your next 2 autos.

Cast The Culling (R) on a target your team has immobilized: each shot hits the first enemy in its path, and you can use Relentless Pursuit (E) while firing.

Look for trades and kills early on: Lucian is strongest early, and his impact drops once the other marksmen have their items.

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.