Plug in adjectives that describe your protagonist, with examples such as "Amazing Spider-Man" and "Incredible Hulk" in mind. Plug in other characters that are integral counterparts to your protagonist, looking to comics such as "Batman and Robin" and "Green Lantern/Green Arrow." Try using only the name of your protagonist to see whether it is memorable enough for readers.
Use the theme of the comic to describe the book. Use phrases that describe what the reader will experience with titles such as "Tales of Suspense" and "Tales to Astonish" as examples. Think about what type of readership you want, and consider how you can give those readers a hint about the subject without revealing too much.
Think about objects or things in the story that allude to your protagonist in a memorable way. Consider examples such as "Sledge Hammer" or "Blood Sword," which provide a source of both familiarity and mystery to readers. Decide on the source of power or interest for your characters and whether that would best describe your comic book in an engaging manner.