Tony Stark : his best friend is Rhodey
Bruce Banner :He has your brother Tony as his best friend
Steve Rogers ; Bucky has been his best friend from the very beginning
Bucky Barnes : Him and Steve will be best friends till the end of the line
Sam Wilson ; Him and Steve have been best friends since they first met
Tchalla : His best friend happens to be his sister Shuri
Clint Barton : His best friend is Natasha and they have been with each other through thick and thin.