Yondu

"'I'm Mary Poppins, y'all!'" Yondu Udonta is the leader of the Ravagers and a major character in the Marvel Cinematic Universe.

Early Life
In his youth, Yondu was sold as a Kree battle slave by his parents for money. He spent twenty years locked in a cage until Stakar Ogord freed him. Yondu soon became the leader of a group of Ravagers, and was hired by the sentient planet Ego to bring his children over to him. However, Yondu did not realize that Ego was killing his children until one day, when he was hired to bring one of Ego's children, Peter Quill. Not wanting Quill to endure the same fate as Ego's other children, Yondu instead took Quill in as his surrogate son and raised him to be a Ravager. During this time, Stakar realized what Yondu was doing and exiled him and his clan.

How Guardians of the Galaxy Should Have Ended
Yondu is first seen on Xandar fending off a group of Sakaarans with his arrow. However, a Sakaaran shoots Yondu as the latter massacres the others.

How Guardians of the Galaxy Vol. 2 Should Have Ended
Yondu is first seen using his arrow to kill his traitorous crew. However, he is shot in the head by one of them.

During the final battle at Ego's core, Yondu is pursued by Sovereigns. Quill suggests that Yondu use his arrow to destroy the Sovereigns' ships, which he does.

Yondu joins the Guardians at the Super Café, where Quill describes the aftermath and realizes that Yondu was his true father. Yondu later joins Groot and Batman during their catchphrase battle, yelling his famous "I'm Mary Poppins, y'all!" The real Mary Poppins then appears, and Yondu is surprised that she is a woman, having believed her to be male.

Villain Pub - The Dead Pool (Infinity War)
When joining Malekith and Iron Monger in countering Joker's claim that all of Marvel's heroes live, Ego mentions that Yondu didn't survive the events of Guardians of the Galaxy Vol. 2.