Cable

While most fans would like to see Deadpool in the MCU, the Merc with a Mouth is so much better without the restrains of a PG universe. So, instead, we believe that Cable would have been a much better addition to the Marvel Cinematic Universe "“ but, as you know, 2018 will bring the mutant's first appearance on the big screen (portrayed by Thanos himself, Josh Brolin) in Deadpool 2.

However, given his backstory, he is one extremely interesting character "“ furthermore, his time-travelling abilities would have been something new in this shared universe. With his tremendous telepathic and telekinetic abilities, with future technology at his disposal, any MCU movie featuring him would have been great.

Even in a more villainous role, going against the Avengers, Cable would have been a great hero in this shared universe (while adapting a storyline such as X-Sanction).