Marvel's version of Loki may be a literal god of trickery and deception, but for one fleeting moment, he really did lift Mjolnir and carry the powers of Thor during a showdown with his corrupted brother. Loki’s always ridden the fence between good and evil, usually succumbing to greed and temptation, but once, he did manage to redeem himself.
In Loki: Agent of Asgard #9, writer Al Ewing and artist Lee Garbett tell the story of Loki’s family blowout that eventually wins him heroic status. Thanks to a spell, the morality of all heroes and villains were reversed, so Loki is trying to reform, making amends for his past misdeeds. The Avengers have run amok, overtaken by anger, but Thor was in a serious crisis. Declaring himself unworthy, he abandoned Mjolnir on the moon near a Kree base. The two brothers, each running against character, seize the opportunity to confront each others’ weaker halves in a battle to show who the true hero is.
Thanks to the spell, Loki gets the upper hand on a rage-blind Thor. He manages to lift Mjolnir, and takes on the powers of the thunder god along with it. What follows is a very personal fight between Thor and Loki, the two adoptive siblings. Loki tries to prove that he has the ability to grow, and Thor argues that his path isn’t as easy as everyone pretends. Loki gets some solid hits on his brother, but before he can do more, the spell is reversed. Thor claims no memory of the incident; Mjolnir lay back on the moon surface.
Through this whole title, Loki is trying to explore his morality. Under direction from the All-Mother, he becomes an “Agent of Asgard” in an attempt to clear his record. Some of his old friends, like Lorelei, don’t like the new leaf he’s turning over, while Verity Willis, (a mortal with the power never to be deceived), is in his corner Meanwhile several versions of Loki -- at different ages, from different realities -- are interfering with who he wants to be right now. While he may not have the answers, comic fans know Loki might never have been evil at all, and fighting off the versions of himself trying to hold him back is an ongoing battle.
Titles like this, entirely devoted to a villain figuring out different sides to themselves are exactly how comics can expand their characters, giving them even more life and longevity. Loki’s trademark is tricks and lies, so, while fun to write and joke about... it makes for a big credibility problem. Why is anything he does serious if he can just undo it in a second? Is there any hero or villain who’s died more often? Loki becoming Thor represents the darkest side of a relationship between two brothers; if his moral ambiguity can explore more of those feelings, he can tell a powerful story.