The basic theme has to do with protagonists turned major antagonists & main villains that were created by a retcon (William Burnside was originally a protagonist and presented as the hero in the 50s before the real Steve Rogers was reintroduced in the 1960s having it to where he was retconned to be a separate person who went mad from the effects of a faulty serum and becoming one of Cap's greatest villains after the real Steve returned and Venom Snake was introduced first as the real Big Boss in Metal Gear 1 before MGSV retconned it to where he was actually a body double who had been made to look & think like the real Big Boss who was working with the real Big Boss to meet their shared goal of Outer Heaven), with both being surgical body doubles of legendary U.S. Soldiers who are major figures in their universes (contrast in that Steve Rogers while he has had his disputes with the U.S. Government ultimately fights for the American people even when it means he has to go against the Government's private interest to do it while Big Boss after the death of The Boss has a hostile relationship with America that lead him to create Mother Base, Outer Heaven, and Zanzibar Land), both having undergone extensive plastic surgery to become the image of this person who they are deeply fanatical to (contrast in that William Burnside's was his own choice and without the real Cap who was frozen's consent while Venom Snake did not consent to it and was brainwashed to think he was Big Boss before accepting his fate and usinf it to serve him as the leader of Outer Heaven), both also becoming a leader in a major terroristic faction that act as antagonists (William Burnside being manipulated to become a leader in the villainous National Force and Watch Dogs as The Grand Director and as an imposter Cap once again and Venom Snake leading Diamond Dogs and Outer Heaven for Big Boss)

I am still somewhat new to Metal Gear so sorry if there are errors

William Burnside (Marvel Comics) vs Venom Snake (Metal Gear). Not sure if I can get the connections done in time so here's the TN my monthly MU & the basic theme