Hopefully, everyone has watched Avengers: Endgame by now and the death of Tony Stark's character played by Robert Downey Jr. took a toll on fans and Marvel Cinematic Universe. Iron Man is the reason why MCU exists in the first place. As a result, the character's exit also has a huge impact.

It seems that Iron Man's sacrifice has created the biggest supervillain, accidentally. It was often indicated that Marvel Cinematic Universe's biggest superhero; Iron Man was basically a "secret villain" in the entire journey because of his own hubris.

Iron Man led several villainous actions inadvertently including Spider-Man MCU series. The superhero was driven by the vision to keep everyone safe with the help of his armor suit. Thanos who was played by Josh Brolin initially had some motivation as he believed maintaining balance in the world to save resources and achieve stopping humans to cause self-destruction.

It's not surprising that Thanos and Iron Man were destined to destroy each other. Tony Stark's arc was completed with Avengers: Endgame where he sacrificed himself for good. When Iron Man put the Infinity Gauntlet on, he might have created one last villain that Avengers will have to fight.

As per the theory of Comic Book Resources, the surge energy released by the Iron Man's suit can create a new version of Ultron. In fact, Bleeding Edge's storyline resembles what Stark wore in the Avengers: Endgame.

In this storyline, the suit is able to develop a life of its own and the Marvel Cinematic Universe might draw ideas from this to go ahead. There is also poetry in which Iron Man gives birth to the next threat for MCU. This threat could be in the shape of the new Ultron.

However, the sub-plot of this arc is complicated and the arc will center a character called Arno Stark. As per the comic storyline, MCU is expected to pursue any two paths mentioned above. The theory seems to be fascinating and if the franchise decides to feature Stark's legacy, then it can drive inspiration from these plots.

There are fans who believe that they haven't seen Ultron yet while the character is voiced by James Spader, which was his only appearance in MCU so far. However, fans are sure that he will be a threat for the Avengers. It seems Avengers: Age of Ultron has not only introduced Ultron but also Vision and Wanda Maximoff.