Thor Odinson

"You know I'm fifteen hundred years old. I’ve killed twice as many enemies as that, and every one of them would have rather kill me, but none succeeded. I’m only alive because fate wants me alive. Thanos is just the latest of a long line of bastards, and he’ll be the latest to feel my vengeance. Fate wills it so."

- Thor

Thor Odinson is the deuteragonist of the Marvel Cinematic Universe. He's the king of Asgard, Odin and Frigga's son, Loki's adoptive brother and a founder member of the Avengers.

He's the main protagonist of the Thor films and the deuteragonist of the Avengers films.

Official Description
"Thor is the eldest son of Odin and Frigga, the King and Queen of the Realm of Asgard. After a brief exile on Earth, Thor joins the Avengers. Upon the passing of his father, Thor becomes King of Asgard, although his world is destroyed by Surtur the Fire Demon."

- w:c:marvelcinematicuniverse:Marvel Studios: Character Encyclopedia

Avengers: Infinity War
Thor was convinced the Tesseract was destroyed on Asgard, but shocked and betrayed that Loki had the stone, and offered the Tesseract in exchange for Thor's life. He watched in horror as Loki was killed before him. He is left in mourning his brother, but soon found the Guardians of the Galaxy.

Thor leaves with Groot and Rocket to get help from Elitri, the last surviving Dwarves. They headed to Earth, where Thor was reunited with Captain America. He attempted to kill Thanos with Stormbreaker to avenge his brother's death, but Thanos snaps and kills off half the universe.