In the ever-expanding world of Marvel Comics, there is only one villain who has remained a constant thorn in the side for the Avengers for years being a constant reminder of their mistakes, and it's not Loki or even Thanos.

It is the super-intelligent A.I. Ultron.

Original "Avengers" director and occasional Marvel Comics writer Joss Whedon even pushed mysterious end credits villain Thanos to the background in favor of the artificial intelligence for the 2015 sequel affectionately subtitled "Age of Ultron". It was assumed that Ultron was arguably even more of a priority for Whedon, who always had an intention to use Ultron for the sequel.

Introduced in the early days of Avengers comics, Ultron was an A.I. created by original Ant-Man Hank Pym as a new technological marvel that had capabilities that rivaled the superheroes themselves. Unfortunately, Ultron would become self-aware and set out to spread his A.I. influence throughout the world with a natural takeover of Earth in mind.

Thus, a new villain is born.

Unlike most other villains, Ultron cannot be bargained with as the android has reasoned with himself that he knows what is ultimately best for humanity, and nothing is going to steer him from that goal.

Following Tom Hiddleston's fan favorite performance as the God of Mischief Loki in the first "Avengers", it presented an automatic challenge for any villain to follow up. Similar to Loki, Ultron shares a personal connection to the Avengers team in that the machine is created by heroes Tony Stark (Robert Downey Jr.) and Bruce Banner (Mark Ruffalo) in the film as a peacekeeping force for good to combat the onslaught of rising threats to mankind.

In the case of Ultron, the Marvel Studios-branded humor was a major culprit. While Marvel Studios' humor is a welcome benefit to the film and characters, the humor unintentionally downplayed the murderous nature of Ultron's character, though there was a suitable story rationale for the humor that Ultron frequently displayed.

Throughout "Age of Ultron", the Avengers tear through Ultron's various different forms throughout the film as if his vibranium-coated body is made of styrofoam. Eliminating a version of Ultron, whether early, the new far more advanced model should have been a challenge. Each version continuing to become deadlier and adaptable than the last.

Granted, it is tricky for a film to establish a villain and make him a credible enough threat while giving the heroes a chance at actually beating him. However, that is what makes the heroes so heroic in that they overcome seemingly impossible odds and live to fight another day.

But not everything the film had set up for Ultron became a disappointment. James Spader ("The Blacklist", "The Practice") was a great choice for the evil A.I. Spader is not quite Morgan Freeman level on the iconic voice scale, but he has a great voice for an automaton that is calm and collected yet contains a hostile nature about him.

Ultron creating his own form of artificial life through future Avenger The Vision was straight out of the comics and connected well with the film's theme of evolution. While Ultron himself was created by Hank Pym in the comics, it made sense to have the MCU designers be characters that the audience would be more familiar with in the current timeline such as Tony and Bruce.

It was evident that Whedon was not looking to translate the comic interpenetration of Ultron to film verbatim, but instead, give a fresh new take on the trope of super-intelligent androids turning against humanity.

Unfortunately, the Ultron depicted in the film is not nearly as memorable or menacing as his comic counterpart or even other Marvel villains. Ultron should be a robotic force of nature that can be weakened and put out of operation temporarily but never truly defeated. Think the calm HAL 9000 computer system from "2001 A Space Odyssey" melded with the ruthless body of the T-1000 from "Terminator 2". Ultron had the chance to be a threat that was truly unique and formidable for the Avengers to go up against.

While it is great that we are living in a time where B to C list comic book villains like Loki, Thanos, and ol fishbowl head Mysterio are now household names, it is a shame that the Professor Moriarty of Earth's Mightiest Heroes is not in the same league as his other contemporaries.