10 Most Powerful Avengers Villains Ever

2. Ultron

To the Avengers, Ultron is like a little annoying fly who won't go away - if the fly was a murderous, super-strong robot equipped with something called an Encephalo-beam.

On top of that beam - which allows him to basically brainwash people - Ultron has a diverse array of technological abilities including flight, concussion blasters, tractor beams, and radiation emitters. Not to mention the aggravating ability to upload his consciousness into countless additional bodies, making it extremely hard to dispose of him.

Ultron is one of the most dangerous foes the Avengers have ever faced, thanks to his limitless ability to upgrade and improve himself and even, in some cases, take over entire alien races. There's a reason one of the worst dystopian futures the Avengers ever faced was one ruled over by Ultron, and you can tell how seriously they take the villain by how much they all brick themselves when he/it turns up.