Doctor Who: 10 Villains The Doctor Couldn't Defeat
4. The Stingray Swarm (Planet Of The Dead)
A swarm of stingrays doesn't sound like a massive world-ending threat on paper, but if you give each of those stingrays sharp teeth that are capable of devouring anything you put in their way, and some armour plating? Things get a bit more tricky.
This is exactly what the Tenth Doctor had to deal with in 2009 Easter special Planet of the Dead, where he had to get a bus full of humans through a wormhole before they were all ripped to shreds by a deadly stingray swarm.
And this proved extremely difficult to do, because there was no way to fight off or even delay the swarm - not even for a minute or two. This was a group of over a billion stingrays, each with those sharp fangs and tough outer shells. If it was just ten or twenty of them, maybe the Doctor could've figured out a way to fight back. But billions of them, all hungry, and all moving at a rapid pace? The only option was to flee.
And so, that's just what the Doctor did. Flying a double-decker bus through the wormhole to the safety of Earth, the stingray swarm was left to fly around the sandy planet of San Helios, uninterrupted, unobstructed, and unstoppable.