Mainly just there to NOT be listened to by Tony Stark, and have a bigger suit and guns but still be shown up during every battle. We also don't learn anything about him outside of being Tony's friend and working for the military/government (and get shut down by them too).
Sam Wilson was very willing to drop everything to be with Captain America for almost five years and in that time, we learned very little about him. Eventually he technically gets his own show, where he continued to costar with a white man who got love interests, while he gets nothing.
Maria Rambeau is Captain Marvel's best friend/ essentially wife/ space fighter. At least Maria has actual family members that are shown, like her daughter, Monica, who grows up to follow in her mother's footsteps and become a Black Best Friend for the Scarlet Witch.
J. Jonah Jameson's right hand man and black best friend. Always there to laugh at his shenanigans and tell him he's wrong, but not actually do anything about it. He has a family but his hard work gets him accused of being an absentee father by his own son.
An original character created to be the Arrow's black best friend and sidekick, Spartan. Diggle is always expected to drop everything for OLiver Queen, his’s own wife convinces him to go on a dangerous mission for Oliver instead of staying home to take care of their newborn baby and later Oliver kidnapped his wife and everyone reprimanded John for being upset about it.
Pete Ross was on Smallville for 3 seasons, but gets no storylines, love interests, background, anything plus he’s black in Kansas so that can’t be super fun. One of the creators felt that he was being wasted and (instead of giving him better storylines) wrote him off the show. Pete guest stars in Season 7, just to be a villain of the week and then hype up Clark some more before never being heard from again.
Ethan Bennett, another original Black Best Friend, made to be Batman's hypeman until he is turned "insane" by the Joker and becomes the villain Clayface. Ethan is then told that he can't be both sane and powerful, Batman even says “In your case, doing good is an act of self-destruction” and that his powers lead to abuse, (which black people get told a lot, topic for another time).
Julio Mendez's main job is to look less professional than Barry Allen and take Barry's offensive jokes about his dreadlocks: “Would you get it through those matted locks…?” Julio does actually have a girlfriend, named Sabrina, but mostly he just complains about her, one of the only times we actually see her, he is flirting with another woman in front of her, so... great representation for black love!
M.M. is Billy's black best friend in The Boys, always the voice of reason but is never listened to, and does very little over than be backup for the others. Although he has a wife and daughter, every season he leaves them to go back to run into gunfights to save the others who all have a death wish.
We all know him. We all love him. We all love the line "Where's my super suit?" but we still don't actually see his wife and none of that love changes the fact that he's a Black Best Friend.
