Juggernaut + Zeus

Why this works

Picking these two heroes together forces the enemy into a difficult itemization choice. Zeus provides a constant stream of magical damage that wears down the entire enemy team from a safe distance. This perfectly sets up Juggernaut to clean up with Omnislash, which is all physical damage, making it tough to build both armor and magic resistance at the same time. Beyond that, Zeus can reveal key targets with Lightning Bolt, giving Juggernaut a clear go-ahead for a pickoff without needing his own detection. The global vision and damage from Thundergod's Wrath also gives Juggernaut the information he needs to farm aggressively or find isolated heroes.

In teamfights, Zeus hangs back and softens everyone up while Juggernaut uses Blade Fury's magic immunity to walk through spells and get into position. Once a priority target is low, Juggernaut can commit Omnislash for the kill. If the fight gets drawn out, Juggernaut's Healing Ward gives the fragile Zeus the sustain he needs to keep casting spells from the backline. Enemies have to respect this threat from the mid-game onward; being caught alone can mean getting deleted by the combination of global damage and a well-timed gank from Juggernaut.