Agents Of SHIELD Season 4: 15 Characters Who Need To Return

Last Seen: Discussing bodily repairs with Fitz and Simmons following his capture and torture by HYDRA in the second season episode 'The Dirty Half Dozen'.

Mike Peterson has been a part of the series from its very first episode, going from Extremis-afflicted father to an emotionless, cybernetic puppet to hero and valuable team ally. From the unveiling of Jiaying's plans to the formation of the Secret Warriors to the conflict with Hive to the arrival of Ghost Rider and LMDs in the world, so much has gone down since Mike was last seen, making it all the more surprising he hasn't turned up to help for any of it.

Over the first two seasons, he grew to be quite an interesting aspect of the show, and one whose appearances always provided something to look forward to, especially when they were unexpected, like his cheer-worthy rescue of Coulson and Hunter from Gonzales' men.

Though he's been left out of being a more stable member of the team and was even excluded from the Secret Warriors roster, Deathlok - locked and loaded with a whole host of new upgrades from his ongoing absence, obviously - is definitely something the show needs more of before it's all over.