Iron Man: Extremis (2010)

When a mysterious, experimental serum called Extremis gets stolen, and the lead researcher kills himself after writing a confession of sorts, Dr. Maya Hansen, the other researcher on the project, calls her old friend Tony Stark for help. After a nearly antagonistic interview by an investigative reporter, Stark gets the call and jets off to Hansen's aid. During a visit to a mutual friend that Stark had hoped would raise Hansen's spirits, it becomes clear that the Extremis was used to transform a government-hating terrorist named Mallen into a killing machine. After Mallen unleashes his hate on a target to test his power, Stark decides that Iron Man must take him down. The ensuing battle pushes Iron Man beyond the breaking point and forces Stark to reassess his entire reason for being a superhero: how far would he be willing to go to stop Mallen?