Axe + Night Stalker

Why this works

Picking these two together is a clear statement of intent: you're going to run at the enemy from the first night cycle onwards. Night Stalker is built to hunt and disable single targets, especially after dark. His silence and slow make it incredibly easy for an Axe to walk or blink in for a guaranteed Berserker's Call. Both heroes want to be on top of the same poor soul, and their kits combine to make that happen reliably. Night Stalker finds the victim and slows them down, and Axe brings the hard lockdown and Culling Blade to secure the kill.

This duo hits a massive power spike in the mid-game. Once Axe has his Blink Dagger and Night Stalker can either wait for night or force it with Dark Ascension, they can take over the map. They'll systematically hunt for isolated heroes, forcing the enemy team to group up and play defensively. This cedes map control and farm, letting the Axe and Night Stalker team build a lead. The main way to play against this is to have good vision, stick together, and try to survive their initial burst. If they can't snowball off mid-game kills, their advantage starts to fade.