Loki was, and still is, one of Marvel's greatest villains. With such an intriguing character arc and most of the time actually having fairly noble intentions, Loki has been a delight to watch in the MCU, going from hero to villain to hero and back to villain before trying to save the universe from Thanos.
Fans can't wait to see Loki in his upcoming Disney+ series, and while Loki hasn't always done the right thing, there are times when he has sacrificed himself for others. There are often ulterior motives to whatever Loki does, such as helping Thor off Sakaar in order to get him captured, but Loki has proven to be a hero when the time calls for it.
Cooperated With "Get Help"
Taika Waititi and Chris Hemsworth put a fresh spin on Thor in Thor: Ragnarok. Even though the film started out with Loki impersonating Odin, by the third act, Loki was on Thor's side.
In the process of escaping Sakaar, Thor suggested doing "Get Help," a move that seemed well-known amongst the two brothers, which involved Loki being thrown into the Sakaarian soldiers. Even though Loki hated it and it was humiliating, he still went along with it anyway.
Went Back To Asgard Peacefully
After a gruesome battle, the Avengers managed to defeat the Chitauri and take Loki prisoner. Despite using the Tesseract to escape in Avengers: Endgame, in the first movie and original timeline, Loki went back to Asgard peacefully knowing he was going to be answering to Odin and likely face time in an Asgardian prison.
Loki could have easily battled his way out or played some sort of trick, but he surrendered and used the Tesseract with Thor to return home.
Helped Thor Fight The Frost Giants
Kenneth Branagh's Thor was certainly a great and underrated introduction to the character. Thor may not have been the hero he is now, and this is what caused the battle with the Frost Giants in the film.
Loki could have left Thor to die, gone back to Asgard with no hesitation, and tell Odin that he narrowly escaped, but Loki stayed to help Thor despite his resentment of his foolish decision to start the war.
Saved Odin's Life
By the end of the first Thor movie, fans learned that Loki was the trickster behind a lot of the film's plot. Yes, he showed the Frost Giants a way into Asgard, but he also saved Odin's life when he was about to be killed by Laufey.
All Loki has ever wanted was to be seen as Thor's equal in the eyes of his father. Loki's desire to be king of Asgard and a king in his father's eyes is what lead him to be the hero.
Helped Thor Escape Sakaar
In Thor: Ragnarok, Valkyrie took Loki prisoner and brought Thor and Bruce Banner to him. While they were figuring out a plan to escape, Loki offered to help as he had stolen the access codes to the Grandmaster's security system.
Even though Loki was planning to turn Thor over to the Grandmaster, he still got him inside the room where the ships were, when he could have easily betrayed Thor at any point before that.
Helped Thor Fight Hela
Loki's trick backfired and Thor managed to put the electrical tag on Loki to render him unable to move. Despite this, Loki made his way to Asgard to help Thor fight Hela and save Asgard from extinction.
Loki could have led Korg and the others away from Asgard, leaving Thor to potentially die on his own, but he chose to help his brother instead.
Tried To Kill Thanos
Thor: Ragnarok led directly into Avengers: Infinity War, with the Asgardian refugee vessel being the target of Thanos' second attack on his hunt for the stones. Thor stated that Loki will always be the God of Mischief, but he could be more.
Then in Avengers: Infinity War, after Loki pretended to pledge allegiance to Thanos, he referred to himself as "God of Mischief...Odinson..." before trying to kill the Mad Titan.
Taking Care Of Asgard
Loki successfully impersonated Odin on Asgard at the end of Thor: The Dark World and the beginning of Thor: Ragnarok. However, Loki's goal was never to take the people of Asgard prisoner and enslave them.
Loki said himself that Asgard was prospering, so even though his methods were less than ideal, as the King of Asgard, he seemed to do a great job at taking care of the world and its people.
Gave Thor A Hug
At the end of Thor: Ragnarok, Loki and Thor had gone through an incredible journey and Loki realized that maybe never seeing Thor again wasn't exactly what he wanted. As they were onboard the refugee vessel, Thor thanked Loki for his help and said he may not be so bad after all.
After Loki's illusion earlier in the film in the Sakaarian prison, Thor didn't believe Loki was really there and said if he was he might even give him a hug. However, Loki caught the item that Thor threw, stating "I'm here." Even though the camera didn't show it, fans can assume the two shared a brotherly hug for the first time in potentially years.
Saved Jane Foster From Death
In Thor: The Dark World, after helping Thor escape Asgard, the two arrived on Malekeith's world where they planned to kill Maleketih and destroy the Aether.
However, a battle ensued when Malekeith absorbed the power of the Aether. As the Dark Elves, threw a black hole-like grenade, Loki pushed Jane out of the way so she didn't get sucked into it. This also came after he covered Jane's body as the Aether exploded, shielding her from the blast.