Glass Shark
Banned
So far the only game I played that undying lost, the enemy randomed drow and clinkz. Even then we newly won. Undying so good.
I have no quantifiable evidence for this, but I think a big part of why Undying is so good is that he's simply demoralizing to the enemy. You can get ridiculous kills when you shouldn't be able to with zombies, and the strength steal makes certain heroes laughable. You can also get first blood at the horn like 75% of the time if you bring an ally and drop a Tombstone at the rune. It's easy mode.