Venomancer + Zeus

Why this works

Stacking up magic damage seems like the goal here, but the timing is often misaligned. Venomancer is all about sustained pressure, wearing enemies down with damage-over-time effects. Zeus, on the other hand, wants to delete a target instantly with a burst of lightning. The issue is that neither hero provides the hard lockdown needed to hold an enemy in place. Venomancer's slows are helpful, but they don't stop a target from using a defensive item or a mobility spell to escape before Zeus can land his full combo. The damage sources end up competing more than they cooperate.

In a real teamfight, Venomancer might land a great Poison Nova, leaving multiple enemies weak and poisoned. The problem is that they don't die from it. This creates a window where they can retreat, heal, or get a spell off. Zeus is then left to clean up with his own spells, but it can feel inefficient. He might have to use his ultimate to finish off targets that are already scattering, instead of using it to initiate a burst on a priority target. The enemy gets to react to two separate waves of damage rather than one overwhelming one.