Rage.Of.Olympus
Senior Member
Ultron - He's more conventially powerful in his higher end incarnations but this might be one of those cases where a skilled magician trumps brute force, even in great numbers. Scarlet Witch has a history of f*cking up Ultron due to being a sorcerer, and I can see Loki winning even against an Avenger wrecking version due to this.
Doctor Doom - Doom's sorcery has been given a pretty large push lately but still not enough to beat Loki. I've probably seen each of Doom's greatest feats and while impressive (Particularly the one with Doctor Voodoo), they simply don't match up to Loki's best. I also got the impression that Loki was more powerful based on their interactions but that's more up to interpretation.
Magneto - Loki is just a bad match up for Magnus imho.