While the God of Mischief has long been an integral part of the Marvel Universe, it wasn't until the release of Loki on Disney+ that fans got a glimpse of just how much unwitting influence the titular Asgardian has had across almost every corner of the Multiverse. However, one of the most accomplished versions of Loki was also the most cruel, and the pain he inflicted on the world before being undone was unforgettable.
Years ago, Thor moved the realm of Asgard to hover just above New York City, which by many was taken as an act of aggression. When Asgard fell, Thor's rage boiled over to the point that he lead an Asgardian takeover of most of the world, starting with annihilating the Avengers and rebuilding Asgard and NYC together as New Asgard. Under Lord Thor's rule, Loki became the Head of World Security, with his first appearance as such occurring in 2003's Thor #68 by Dan Jurgens and Scot Eaton.
After Jane Foster's support of the growing separatist movement and aid rendered to the then-pregnant Scarlet Witch was revealed, both Foster and Wanda Maximoff were taken prisoner and brought before Loki to answer for their crimes. This resulted in their being subjected to "processing," a form of reconditioning that boasted remarkably low survival rates, and which cost both former heroes their lives. As brutal as their fate proved to be, it was not the worst thing that the Loki of this future did, and he had over a hundred more years to perfect his terrifying craft.
In the far away future of 2170, Lord Thor's reign continued on, as did Loki's place in it, one which he had no intention of losing. When Thor's son Magni became infatuated with a human thief named Jordahl, Loki presumed that their budding relationship might lead him to further answers regarding those who wished to undo Asgard's seat of power. While the real Magni fought in Asgard's name and became disillusioned with its conquest in the process, Loki took his form had Jordahl and her family stolen away for processing. Loki's focus on perceived threats ultimately served to distract him from real ones when an attack on the royal family finally came in the form of Wanda's adult daughter Kya alongside the other resistance forces and even Thor's own former ally Thialfi.
When their attempt on the throne failed just as Thor was entering the restorative Odinsleep, Loki was left to decide the fate of the would-be usurpers. The cruel tyrant's judgment came in the form of public executions, Thor's defense of which were only another reason for Magni to turn away from his father. When Magni finally stood up to Thor with the power of Mjolnir in hand, their personal conflict was cut short by the arrival of another threat to the kingdom in the form of Desak, Destroyer of Gods. As Head of Security, Loki had was prepared for such a powerful enemy, even if his plan of action would ultimately prove to be his own undoing.
As Desak unleashed his own wave of destruction upon New Asgard, Loki unveiled his secret weapon in the form of the Destroyer. This mythical weapon needed a soul to pilot it, and Loki had chosen that of Tarene, better known as Thor Girl. Created to help mortal beings ascend to a higher consciousness, Tarene's soul was tormented by her imprisonment in the Destroyer. Once she was freed there was little left for Loki to do but try and explain away his duplicitous actions as necessary for protecting Asgard's place on Earth.
Loki begged for Thor to strike down all who opposed Asgard so that it could rise to subjugate them, but this act only further soured his standing among the rest of those who remained. In his final act of defiance Loki tried to fell Tarene's spirit, only to be obliterated by her in return. Not long after Loki's death in this timeline Thor would find the means to go back and set things right, giving both of them a chance to do better.