I know, that pun was awful. But it got your attention, right? Now that I have drawn you in, I want to talk about another missing central figure that I feel deserves to join the MCU. Today's candidate: The Grim Reaper. The Grim Reaper has a robotic arm with a scythe attached to the end of it, from which he derives his name. He frequently appears in tv shows and comics, has ties with Hydra and is definitely one of my favorite supervillains!
I love the character of The Grim Reaper, but I'm not a huge fan of the above incarnation of his outfit. I think that if the MCU were to use him, he should instead be attired in something similar to his outfit from Avengers: Earth's Mightiest Heroes, shown below.
In his first appearance (The Avengers #52, May 1968) Reaper originally had no superhuman abilities and was only a tech-based villain whose scythe had numerous capabilities. In more recent times however, his abilities have been altered to include the power of reanimating the dead, teleportation, the creation of illusions, and clairvoyance, all of which are things that need to be in the MCU... like yesterday. And the fact that introducing Grim Reaper would pave the way for introducing his brother Wonder Man is just one more incentive!