Considering the fact that Loki was never ACTUALLY KO'D in the movie I'd say he takes this. None of them have the strength or power to put down a being that took a one sided beating from the Hulk and still lived albeit he was pretty hurt. With his staff he can effectively take control of some Xmen (maybe Iceman and Colossus) and even the odds a little more. The Xmen don't have any knowledge or prep to handle this extremely powerful being who uses illusions and magic on top of being physically more powerful that can shoot energy blasts that can match a lower level cyclops optic blast with ease. Not to mention he can take over their comrades. Loki takes this with some difficulty
Loki kills them all, except Wolverine, for obvious reasons. Though Wolverine would make for an excellent servant. Loki would do exactly what he did to the SHIELD agents in the beginning of the Avengers movies. None of the X-men, besides Wolverine and maybe Colossus, have shown the durability required to take a hit from Loki, nor the speed. Jean Grey is a non-factor, since she hasn't done anything to suggest she would be of much use. Storm requires time to use her powers, and has been nearly beaten by a speedster and Toad. Colossus has not shown he could withstand a disintegration beam from Loki's staff and Wolverine would be incapacitated. Bobby is another non-factor, he's a teenager, who didn't show the level of power or skill compared to his comic version, and would be too slow to even react to Loki's attacks. Cyclops would not fair any better, since neither his h2h or reactionary speed would be able to match Loki's. Loki is an Asguardian, well versed in combat and killing people, with illusion casting abilities, a mind control device, that also acts a disintegration beam, versus, a bunch of mutants, most of whom are non-combatants, who pretend to be heroes. To be quite frank, Wolverine would be the only one standing after Loki decides to kill them.