In Thunderbolts*, Bucky will prove key to branding this group of characters together. In that same scene, Valentina Allegra de Fontaine assigned Yelena to kill Clint Barton, a.k.a. Hawkeye ...
The Thunderbolts have been a long-awaited MCU team. The quasi-villainous anti-hero/misfit gang is a staple of the Marvel Comics world, and many heroes have been a part of it at some time or another.