1. Loki Destroyer
2. Eh, Destroyer was destroyed by its own power, which leads me to believe that as a creation of Odin, which was also stated as containing the same cosmic energies as Mjolnir in movie canon books/bio description (which admittedly isn't the best or most reliable source of information, but it does show creator intent to a degree), only similar sources of power would render it inoperable. Not sure how Parallax would hurt it as its main course of attack is soul/fear drain and the Destroyer in the movie was depicted as being like an empty construct. Conversely, Parallax, while it could be injured, and by stuff that really shouldn't have effected it, regenerated quite a bit and it took burning in the sun to defeat it.