Marvel’s Loki has a long list of people he’s wronged, but his crimes against Lady Sif in the comics are much worse than any in the MCU.
Although Loki enjoys meddling with the life of his adopted brother Thor, the god of mischief isn’t above including other Asgardians like the warrior Sif in his usually nefarious plans. While the MCU’s version of Sif had a rather specific grievance with Tom Hiddleston’s Loki, her comics counterpart has a greater history and even more reason to distrust and even despise the infamous trickster. Loki had once stolen Sif’s body for his own agenda while trapping her spirit inside a human body, which was slowly dying while being unaware of who she really was as Loki watched from the shadows.
After the events of Ragnarok, J. Michael Straczynski’s Thor saw Dr. Donald Blake travel into “the Void” to find his famous alter-ego. Convinced that with Ragnarok completed he could rebuild Asgard and bring back its people, Thor fought to be reunited with Mjolnir and soon returned to Earth. After relocating Asgard to Midgard, specifically Oklahoma, the former Avenger began his journey around the world to find his friends and allies who had been unknowingly trapped in human bodies. After reuniting with others like Heimdall or the Warrior’s Three, Thor was able to find Loki who had taken on a female form. Although naturally suspicious considering their history, Thor chose to give his sibling a second chance at a new life with stern warnings of repercussions should old behaviors resurface.