Aphelios vs Sivir

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.

Dodge Boomerang Blade (Q), then its return: it damages on the way out and on the way back, and it costs Sivir a lot of mana.

If you have CC, cast a cheap spell first, or fake a step forward: Spell Shield (E) only blocks one ability, and heals her if it blocks.

Back off when she casts On The Hunt (R): her whole nearby team gains move speed to engage on yours.

Don't leave her alone on a lane for too long: with Ricochet (W), her autos bounce between minions, and your wave, then your tower, fall fast.