Source: comingsoon.net

14. Ultron

Smart, vicious, and completely terrifying, Ultron has always been one of my favorite Avengers villains.

While the MCU version was a bit more human than I personally would have liked, he was still smart and strong. Ultron is ultimately the best depiction of the most frightening concept in all of AI theory: The Singularity. Simply put, the Singularity is the idea that once computers figure out how to upgrade themselves better than we can, machine intelligence will blow past human intelligence.

Not only can Ultron upgrade himself, he can also build his own robot children, like The Vision. Ultron is also just straight-up terrifying. That robot jack o'lantern look is among the most iconic supervillain designs of all time.

Ultron is fast, strong, and durable. At times, he’s also capable of flight. He can shoot powerful laser blasts, and is able to transfer his consciousness from body to body.

Power Level: Exterminate!

                                               Source: comicvine.gamespot.com

13. Ronan the Accuser

I like Ronan. He’s easily the most underrated aspect of the first Guardians of the Galaxy flick. He's an intimidating villain in his own right, and with his big-ass murder hammer, he's even scarier.

Comic book Ronan is even more well-developed. Dude once tried to use Ego the Living Planet as a weapon. That is some hardcore improvisation, right there. Ronan usually operates on behalf of the Kree Supreme Intelligence, as a big head in a bigger jar that controls the Kree race. Ronan is an Accuser. The Accuser, in fact. This means that he works as an envoy for the Kree's best interests. Usually, those best interests are pursued by using a big space hammer to beat someone's brains out. Ronan is good at this.

He isn't always a villain, though. He sides with the Kree, and when the Kree want good things, so does he. He will diverge from the Kree's best wishes, but only rarely.

Power Level: SPACE HAMMER.