Medusa + Venomancer

Why this works

Stacking Poison Nova and Stone Gaze can put the enemy team in a bind. Once Venomancer applies his ultimate, enemies are forced to either run away while slowed and taking damage over time, or turn to fight and get petrified by Medusa. In either scenario, they're stuck taking heavy area-of-effect damage. Medusa’s Split Shot can then clean up multiple low-health targets that Venomancer has softened up across the fight, making the combination seem effective at controlling a teamfight.

The core problem, however, is a clash in game tempo. Venomancer excels at applying early and mid-game pressure, forcing fights and pushing towers with Plague Wards. Medusa needs a lot of safe farm and prefers to avoid conflict until she has several core items. This often leads to a disconnect where Venomancer's pressure peaks too early, before Medusa is strong enough to capitalize on it. The duo also lacks the hard, instant lockdown needed to secure kills or peel for Medusa, leaving them vulnerable to coordinated aggression before their big teamfight ultimates can be used together effectively.