Just rewatched Winter Soldier and noticed how they foreshadowed Rumlow eventually turning into Crossbones with the his overlapping gun straps creating an X similar to the one he wears in Civil War. :
Marvel's Most Underrated Villain in the Cinematic Universe | Creamer's Cinema Craze
Brock Rumlow (@BrockCrossbones) | Twitter
Brock Rumlow | Hail Hydra Wiki | Fandom
The Falcon vs Rumlow/Crossbones - "This is Gonna Hurt" | Captain America: The Winter Soldier (2014) - YouTube