Monkey King + Venomancer

Why this works

Teamfights tend to fall apart because these heroes pull the engagement in two different directions. Monkey King needs to get on a target and stay there, building up Jingu Mastery for a big burst of damage. Venomancer, on the other hand, deals his damage slowly over time and wants enemies to run around while his poison ticks them down. This fundamental conflict in timing means that neither hero properly sets the other one up. The slows from Veno are not enough lockdown for MK, and MK's all-in commitment doesn't help Veno's kiting style.

This dynamic plays out poorly across the map. A target hit by Venomous Gale can often still walk away from Monkey King before he can secure his stacks and land a stun. The ultimates are another example of this problem; Poison Nova makes enemies want to scatter, while Wukong's Command is most effective when they are forced to stand their ground. Instead of one hero enabling the other, they each try to execute their own plan on the same targets, leading to scattered damage and fewer secured kills.