This is just my destiny so come with me.
Oh god, this scene. I CAN’T.
I mean, it’s become obvious at this point that Loki thinks he’s beyond redemption. His little speech to Natasha earlier, that wasn’t just for her. Loki’s words are never just about or intended for the person he’s talking to. He’s the Liesmith, the wordsmith, the silvertongued (why the hell else would they gag him at the end, when restraints would work just fine?) Loki’s words are his weapon: he manipulates and twists and pushes, but the greatest lies contain just a bit of truth.
He tells Natasha that there’s no way to wipe her ledger clean. There’s too much blood, too much death. Do you think you can ever truly pay for that?
Do you think he’s only talking about her?
What has also become clear at this point that, whatever has happened to Loki, he is in great debt to his new allies. He owes them, and he owes them BIG, and if he doesn’t pay they will tear him apart and make him beg for the end. Chances are, Thanos is going to get his hands on that tesseract whether Loki gives it to him willingly or not. One way ends with Loki having the throne that he was raised to believe he was entitled to. The other way ends with Loki broken and in agony. If both paths lead to the same destination, and if (as Loki believes) there is no hope of redemption for him, then the costs and the sacrifices do not matter. He does what needs to be done because he is “burdened with glorious purpose.”
And so he keeps pushing. He pushes Thor away, repeatedly, with his words. He goes so far as to try to kill him…while knowing that Thor is both strong and capable enough to avoid that fate. Tony was right: Loki didn’t want them dead on the helicarrier. He wanted them alive and pissed and ready for the epic showdown. And Thor is hurt and angry. The moment he pauses, hand outstretched to Mjolnir is, I think, the moment he realizes that he may actually have to kill his little brother.
Which leads to this scene. Thor offers forgiveness one last time, almost desperately - he gives Loki an out. Because before Thor acts, he has to know that Loki has been given every chance to put an end to this madness. There’s this horribly sad and confused look on Loki’s face when he realize that, even after all this, Thor is still willing to offer redemption, and maybe if things were just a little different, Loki might even have been able to grasp onto that.
But what Thor doesn’t know, what Loki tries to tell him as he describes the new and terrible places that he’s seen, is that Loki can’t. This path, or death: those are his only two options. When Loki tells Thor that it can’t be stopped, it’s not stubbornness or pride. There’s a raw honesty, desperation, even fear, in Loki’s eyes. He’s trying to manage the chaos while doing his best to convince his stubbornly, stupidly sentimental brother that all of this is exactly what he wanted (even as his skittish glances toward the city suggest that probably isn’t 100% true)
And so he pushes Thor away one last time, not with words or grand gestures, but with something that Thor can really understand: brutal and intimate violence. Someone else pointed out that Loki, of all people, would know all the weaknesses in Thor’s armor. If he wanted Thor dead, then he’d be dead. The wound isn’t meant to be fatal: it’s meant to be final. The final word. There is no hope for Loki.