Kieron Gillen is approach must-read status with me. I loved his take on the evil trickster in this one shot. While it was somewhat unnecessary, at least Loki's goals and manipulations provide direct background on his actions in the Marvel U and Siege.
Loki is so desperate to make sure that he's free of the curse of predestination and Ragnarok that he manipulates multiple factions to make sure he's master of his own destiny. He enslaves some undead Asgardian spirits with some nice swordplay, he convinces Hela that she needs her realm back immediately, then he arranges to get that realm from Mephisto in exchange for the spirits. It's a great bit of misdirection as he gets everyone involved to do what he needs them to do. Mephisto is totally aware of it, and I loved how Gillen had Mephisto go along not because he was being conned, but because Mephisto loves seeing a master at work. Loki is a bad guy, but he is a bit charming here.
Jamie McKelvie's pencils are so expressive this was a lot of fun to read. He gives the characters their iconic looks but his style makes them seem more... realistic even while maintaining a cartoony look. There are a couple panels where Loki seems to look out at the reader that were a lot of fun.