Okay so Superman is, as everyone knows, one of the most op characters in all of DC Comics. So today I've pitted him against people who have the magic to kill him, from the Marvel 616 Universe.
1) Character doesn't have to be still alive.
2) All characters will wield some type of magic
3) Enjoy this article! :)
1. Doctor Doom
I think Doom could beat Superman because he's skilled in not just tech, but also sorcery because his father was a scientist and his mother was a creepy magic gypsy lady. And being the ever devoted kid he was, after his parents died, he vowed to master both science and magic. So he knows literally every form of sorcery due to travelling back in time and mastering them before those mystical ways were lost in time. So that and partnered with his will to survive he'd be willing to kill Kal-El if necessary or not.
2. Dr. Strange
I'm positive that Dr. Strange could easily beat The Last Son of Krypton in a duel because all of his magical knowledge coming straight from the Ancient One, who is one of the oldest beings in the Marvel Comics who knows a ton of older magic tactics that had been lost in time. His origin story includes him having broke both of his hands and the only "cure" was to climb the Mountains of Tibet and get training in the mystical arts from the Ancient One. If absolutely necessary he'd kill Superman or trap him in the dark dimension.
The reason I think Thor Odinson can best Superman in combat is simply because of two things. One, Thor is powered by his mystical uru metal hammer, Mjolner which can produce wind , thunder, and lightning as well as dimensional rifts ( see Avengers #16 1963) . Two, he's got centuries of battle experience thus if Superman were to do something unexpected then Thor would most likely expect it and in the end not hesitate ending his overpowered life.
Some of Loki's godly ablities include shape-shifting (able to gain the basic natural abilities inherent in each form), astral projection, molecular rearrangement, eldritch energy blasts, illusion casting, flight (via levitation), telepathy, hypnosis, and teleportation. Most likely Loki would make a ton of astral projections of himself, turn himself into Lois Lane to trick Clark, then when he's off his guard turn into him then kill him in his own form.