Marvel’s Thunderbolts needs to make sure that the new superhero team avoids breaking one big MCU rule. While not much has yet been revealed about the plot of Thunderbolts, its main cast has been revealed. Composed of Bucky Barnes, Yelena Belova, U.S. Agent, Ghost, Red Guardian, and Taskmaster, a key defining trait of the Thunderbolts in the comics is that each individual is a reformed supervillain of some sort. The team of anti-heroes will be the first of their kind in the MCU timeline.
https://screenrant.com/mcu-thunderbolts-movie-anti-heroes-rule-break/