Originally Posted by SlackBrian
The thing that sticks out in my mind about that scene was the mocking tone Loki said "sentiment" with. I don't recall any tears, but I can't say for sure if there weren't any. But his tone and attitude didn't seem to suggest a conflicted nature about what he was doing.
Edit: Just watched the scene again. Yep, there was definitely a single tear that rolled down his cheek after he stabbed Thor and said "sentiment". So, hooray.
That one little tear I put down to Loki realizing that he was in too deep to back out and save himself rather than any sentiment
he felt for his brother, save contempt. When Thor appealed to him to stop the attack on Earth, the look on Loki's face was one of sheer panic. The weasel knew that Tony Stark had been right, that there was no possible way his schemes would culminate in his taking the imaginary throne on Earth. And his bargain with Thanos had to have been on his mind as well. The Other had already warned him of the tortures he could expect if he failed to deliver the Tesseract. Loki's tear was for himself and no one else.
Remember, not only had Loki stabbed Thor mere seconds before that self-serving, self-pitying tear rolled down his cheek, he had also just hours earlier sent his brother on a six-mile plunge in hopes of killing him. And prior to that Loki actually did succeed in killing Thor with the Destroyer. When he discovered that his brother had been revived, his reaction was fury, not relief.
I am not arguing that Loki is not conflicted, or that he doesn't have deeply twisted motivations for his evil acts. But I do think that much of his internal conflict is inner directed, that it centers on himself and his feelings rather than on others or the damage he inflicts on the world around him. Loki will never feel genuine remorse for hurting anyone because he doesn't place any value on any life but his own. He killed thousands of human beings during his invasion, something that I definitely think made him irredeemable. He will be redeemed, of course, or pretend to be in order to dupe the ever-gullible Thor once more. Perhaps one day Loki will sacrifice himself to save Asgard in a parody of nobility, but only with an ulterior motive.