Doom + Zeus

Why this works

Casting Doom on an enemy sets up a simple kill. Zeus can then use Thundergod's Wrath to finish that target off, even if they manage to escape the initial fight. On paper, this is a global ganking tool. The issue is that both heroes are committing their longest cooldowns to a single kill. Doom's ultimate already shuts down a hero completely, so if any allies are nearby, the extra damage from Zeus is often not needed. It can feel like overkill, using two massive spells where one well-executed gank would have worked.

Throughout a game, this combo relies on finding isolated targets away from their team. If Doom can catch a key core farming alone, the global follow-up from Zeus guarantees the kill and creates an advantage. The problem arises when the enemy team stays grouped. Using both ultimates on a single hero during a full teamfight can be inefficient. The rest of the enemy team is free to act while Zeus and Doom have spent their biggest resources, potentially leaving their own team vulnerable and lacking the tools to win the wider engagement.