Possibly. I did try to hunt down the name a couple of years later for a ranty blogpost about the prevalence guns in movie posters (as it happens). I looked at the posters for Megamind, but none matched well with my memory of the image or the tagline.

Understood, and agreed, on plot of Megamind and requirement for stereotypical bad-guy-with-gun origin story, but I think my underlying point survives. Even if this was the movie / poster -- smartest entity in the universe shouldn't require a gun (or at least would be ashamed enough to not be waving it about).

The idea that powerful / influential (regardless of good/bad alignment) people as portrayed in our pop-culture need to be seen to be holding a gun is regrettable. If you haven't already, start taking a note of movie posters and the ratio of guns:no-guns -- obviously ignore the romcoms etc genres.