Malphite & Caitlyn Synergy

Playing the duo

Unstoppable Force knocks every enemy in its area into the air, and airborne champions cannot move or dodge, so Caitlyn can place a trap directly under a knocked-up target; the trap adds another 1.5 seconds of crowd control and grants her an empowered Headshot at double range.

Unstoppable Force(R) reaches farther than Caitlyn's normal attack range, and Headshot(P) can reach farther against a trapped target; coordinating the follow-up lets Caitlyn contribute without walking into close range.

How to play as Malphite

Aim Unstoppable Force on targets Caitlyn can reach, not on the enemy back line far past her; if assassins jump on her instead, holding R as a defensive knockup on top of her keeps her alive to trap and headshot whoever is diving. (Unverified: no source confirms this note.)

How to play as Caitlyn

After Malphite lands Unstoppable Force(R), place Yordle Snap Trap(W) where the target will land or retreat; if it springs, follow with the empowered Headshot(P) and use Q when the line is clear.

Around objectives, poke with Caitlyn's range while Malphite holds the front, and pre-place traps on likely approach paths; adjust to where his engage actually lands rather than assuming every enemy will enter a trap field.

Sources

These notes come from LoL Wiki, r/summonerschool, and r/leagueoflegends, checked against the champions' abilities.