It looks like the most interesting rivalry in "Captain America: Civil War" might not actually be between Chris Evans' Captain America and Robert Downey Jr.'s Iron Man. Most fans have been raving about the hilarious dynamic between Sebastian Stan's Bucky Barnes/The Winter Soldier and Anthony Mackie's Sam Wilson/Falcon, who are both vying for the role as Steve Rogers' BFF!
Steve + Bucky = #Stucky
Bucky Barnes may have been Steve Rogers' childhood best friend, but things changed in "Captain America: The Winter Soldier" when Cap discovers that Bucky is actually a Soviet assassin brainwashed by HYDRA. However, their relationship is slowly healed in "Captain America: Civil War" (via Bustle) when Steve decides to defend Bucky from the Avengers.
What About Falcon?
Sam Wilson is obviously Steve Rogers' new BFF as he supports Captain America in his rebellion against the Sokovia Accords. But Falcon is also unhappy with Bucky, since there is a possibility that The Winter Soldier could snap anytime. Nevertheless, they form a tense alliance as part of Team Captain America. Although they bickered over who gets to ride shotgun and battle strategies, Bucky and Falcon still couldn't help but agree that Steve made the right choice by kissing Sharon Carter aka Agent 13.
Bucky v Falcon v Spider-Man
Bucky and Falcon's best moments in "Captain America: Civil War" were their fight scenes with Tom Holland's Spider-Man. The pair teamed up to take on the young webslinger, and they were equally annoyed by Spider-Man's constant talking. In the end, it looked like Bucky and Falcon may have finally become friends, but Sam still insists that he hates Bucky.
"Captain America: Civil War" also teased upon the relationship between Elizabeth Olsen's Scarlet Witch and Paul Bettany's Vision. There is a possibility that the comic book couple might end up getting closer in "Avengers: Infinity War - Part 1" and Part 2.