Story: Avengers, vol 1, #78
Background: Not much of one. M'baku ambushes Captain America in some dumb villain scheme involving the Lethal Legion after he was banished from Wakanda for his failed coup attempt.
The Challenger: Captain America is well... Captain America. We all know that... comic book peak human, shield, ect. M'baku is powered by the blood of the White Gorilla. He is typically just past comic book peak human strength. This is only his second appearance in the comics. In his first appearance, he beat up Black Panther pretty good before succumbing to being an idiot. You can see that fight here: http://blackpanthermarvel.blogspot.com/2016/10/tchalla-vs-mbaku-round-2.html
[Scan Tip: Click to enlarge the images and they are easier to read. You can scroll through them all that was as well. --- Shadow]
No fear Captain America fans... Quicksilver and the Vision saved Mr. America. The other Avengers attacked M'baku, who had to make a quick getaway.
Ahhh... the days M'baku wasn't a complete joke. His first two appearances, he beat up T'challa (and then accidentally smashed himself lol) and then beat up Captain America. His next thing was beating T'challa again via the infamous Monica mannequin.