Source: moviepilot.com
8. The Sentry
Whom? The Sentry was Marvel's attempt to grim ‘n’ gritty-up Superman for the Marvel Universe. He appeared as a classic hero everyone had forgotten about.
Honestly, given the character, that makes a lot of sense. He's very forgettable. It turned out that he was actually a drug addict who broke into a lab and ingested a secret formula that gave him superpowers.
Why He'll Never Appear: Turns out that the best solution Marvel had to the question How do we make Superman a "Marvel" character? was I dunno; give him a mental illness? The Sentry is just a phenomenally uninteresting character, but they kept trying to hook people into liking him.
They made him an Avenger. They made him kill Carnage. They killed him and brought him back as a Horseman of the Apocalypse. Nothing stuck. And the MCU does tend to ignore boring characters from the comics. That's why Gilgamesh hasn't had a movie yet.
