1. Loki shape-shifts into a shark wielding steel rods and defeats Despero.
2. Loki uses the Norn Stones to blow out the Flame of Pytar and defeats Despero.
I know Loki would never fight hand-to-hand against the likes of Despero, so he'd most likely stay intangible until he can get a spell off. So his main weakness there would be his mind I'd imagine.
If Loki doesn't have feats of shrugging off strong TP attacks then I see him going down.
^ Absent battling Odin in astral form, Loki's never been bested in psionic combat. Then again, he hasn't had many psionic encounters. It's fair to note that he's never been mind-controlled or mindphucked to my knowledge though. He's proven immune to Enchantress' charms and immune to Controller's slave discs which were augmented by Thanos' tech if that's any indication. They each have unique abilities but taken together, they've been used to provide considerable amps in power: