In Avengers #11
, Coulson is shown to be speaking to a mysterious character whose identity is never revealed. Apparently, Coulson captured him and is now explaining his plan (the true sign of any good villain) and how his outlook on superheroes changed after returning from the dead. According to Coulson, having his death ordered by Captain America was an eye-opener. He even makes a reference to his MCU counterpart's hobby of collecting Captain America trading cards. He claims he "grew up" shortly before his death, and realizes that he had made a mistake in idolizing superheroes - adopting a hateful stance that puts J. Jonah Jameson to shame.
After accusing his prisoner of being a spy for Black Panther, the current leader of the Avengers, Coulson takes his hatred a step further by executing the man in cold blood. In doing so, Coulson has given up his status as a hero to become the Avengers' next biggest villain. While Coulson is just one man, he certainly has the resources to pose a threat to Earth's Mightiest Heroes, even though their ranks include Thor, Hulk, Iron Man, Captain Marvel, and Captain America. Coulson isn't acting alone. He's being backed up by the Squadron Supreme, a team of heroes who were originally based on members of DC's Justice League. Coulson's Squadron Supreme are operating under the Avengers' radar, and could strike when they least expect it.
Coulson's turn to the dark side is a huge leap for the character. Being a S.H.I.E.L.D. agent with a child-like adoration for Captain America and the Avengers was a major part of his appeal in the movies, and at least in the comics, Marvel appears to be moving away from that image.