Unrequited love seemed to be Loki's "thing". Everyone Loki grew to love, friend wise and beyond, had been mostly one-sided. One example was Odin. Many would argue that Odin loved Loki as his own son, but Loki had felt that Odin felt differently towards him than he did Thor. He had felt this long before he discovered he was a frost giant, and finding out Odin only took him to be a pawn ... as collateral, well that sealed Loki's suspicions. Loki loved Odin as a father and Odin loved Loki as a piece in his game.
Loki's love for the Warriors Three was another example. He wanted to be friends with them and he had grown to love them - Sif included, until he realized that they were only Loki's friend because of Thor. If you took Thor away, Loki would be nothing more to them then a problem. Loki had no doubt that the Warriors Three would hurt him if Thor had no problems with it.
All these things happened when Loki was a young boy. He had always loved those who didn't love him back. Father loved his pawn, Warriors put up with him ... Loki guessed this to be the reason he was so cold towards everyone. If you shut down and refuse to grant anyone access to your heart, you can't be hurt. Loki liked to think that he also had no time for such foolish feelings. Love is for people who need others to be happy and not for someone as wise as he was.
The final example was Thor. Oh, how Loki loved Thor. When thing were happening with Thor and his banishment, Loki had informed the Warriors Three and Sif that he loved Thor more dearly than any of them and he was not lying. Of course they all assumed he meant he loved Thor in a brotherly way instead of its true meaning, but Loki couldn't tell them he loved Thor in a very unbrotherly way.
He had tried everything to make the feelings go away: curses, spells, medicines, herbs, avoiding Thor, distancing himself, being cruel, self torture, different drinks and foods. Nothing worked. Loki had thought that Thor being in Midgard would be enough, but it wasn't. Loki thought about what to do for a long time before the answer hit him. The only way Loki could move on from Thor was to either die or have Thor die.
Loki had looked at the pros and cons of his death and Thor's and found that Thor's death would be better. Thor's reckless ways would get Asgard into trouble, as it had done previous, and Thor would fight when the best thing to do was talk. No, Thor would be an awful king to Asgard. Loki knew he fit better for the "job".
Sitting on the throne didn't feel right to Loki, but he would never admit that to anyone. Looking forward Loki took a deep breath and nodded, readying himself to seal Thor's fate.
"Destory everything."
Loki's words surprised even him. Destroy "everything"? Loki sighed, hoping that no one else noticed his choice of words. Loki watched as his brother, the love of his life, was knocked to the ground. The panic, pain, and regret started to bubble in his chest almost immediately.
"Stand up, Thor," Loki heard himself whisper.
The seconds Thor stayed still felt like hours, but Loki breathed a sigh of relief as Mjölnir shot into Thor's hand.
Looking away, Loki knew that he could not destroy Thor and that even though he was the better king, Thor would have to do. It was clear what Loki had to do and sitting back on the throne Loki realized that he was okay with it. Someone as sick as he was didn't deserve to live anyway.