Muerta + Sniper

Why this works

Setting up for a teamfight, both Muerta and Sniper want to occupy the exact same spot: far in the back, protected by teammates, with a clear line of sight to unload damage. Their kits have some minor helpful overlap; Muerta's Dead Shot can fear an attacker off Sniper, and Shrapnel can hold enemies in place for her abilities. The core problem is that neither hero provides the frontline presence or hard lockdown that the other desperately needs to feel safe. They are both fragile, farm-dependent cores who need another player to create space and absorb pressure.

This shared weakness puts immense strain on the rest of the team. Your other three heroes must provide all the initiation, durability, and saves. Against lineups with multiple heroes that can dive the backline, it becomes almost impossible to protect both carries at once. One enemy will inevitably break through and burst down either Sniper or Muerta before they can get their damage off. The success of the duo relies entirely on the other picks compensating for their similar vulnerabilities.