Iron Man
More than a decade after Iron Man catapulted from Marvel's D-List to “Tony Stark is now synonymous with Robert Downey, Jr., and even projects produced after Iron Man's death are about him,” it's wild to consider how the hero has come. The first Iron Man was a nightmare to make, and early Cracked pieces even debated Iron Man vs. Batman (tagline: Dawn Of Money). The fact that that debate can now be expanded to include things like box office figures and cultural impact speaks volumes to how successfully this minor character launched the MCU.