Lifestealer + Wraith King

Why this works

Thinking of them as two redundant melee carries is the wrong way to look at it. The reality is they create an incredibly durable frontline that forces opponents into a no-win situation. Lifestealer can use Infest on Wraith King, hiding inside a hero who already has a built-in second life from Reincarnation. When the enemy team finally commits the spells and damage to kill Wraith King, a full-health Lifestealer emerges into the fight. This forces them to deal with two major threats back-to-back, often after their key abilities are already on cooldown.

This dynamic comes online in mid-game teamfights. Wraith King can walk in, stun a primary target, and absorb an enormous amount of punishment. Once he finally goes down and Reincarnates, Lifestealer can emerge, use Rage for magic immunity, and clean up the scattered, weakened enemies. The only real counter-play is to try and burn all of Wraith King's mana to disable Reincarnation, or to have enough disengage to kite both heroes separately. Without a specific answer, most teams get overwhelmed by the sheer survivability of the pair.