Kunkka + Magnus

Why this works

Putting Empower on Kunkka sounds powerful, but the two cleave effects don't combine. Since Kunkka’s Tidebringer already gives him a massive cleave, the cleave from Magnus's spell is largely wasted. The bonus damage is still helpful, but a huge part of what makes Empower strong is giving a hero a farming accelerator and area damage they wouldn't otherwise have. On Kunkka, that benefit is missing. Magnus provides a much smaller boost to Kunkka than he would to a different melee carry, making the laning and farming phases less efficient than they appear on paper.

Their teamfight plan can also be a bit rigid. A good Reverse Polarity provides an easy setup for Ghostship and Torrent, but both heroes often want to be the primary initiator. They compete for similar farm priority to buy items like a Blink Dagger and occupy the same kind of space in a fight. If Magnus fails to find a good RP, Kunkka might be too far away or unprepared to offer a different angle of attack. This leaves the team reliant on a single, telegraphed combo that can fall apart if things don't go perfectly.