A/N: Warning for character death.
"What are you prepared to do?"
The question resonates in Thor's mind long after Fury asks it of him. What is he prepared to do in terms of his brother? Thor's original plan, to stop Loki's madness by bringing him home has failed. It was never a realistic plan, but Thor has never been one for realism. He believes in feelings, in the magnetic pull between two people, in the deep ache in one's chest, even in the painful constriction of elation. He is a warrior, but he is a man first, and his love for Loki is only matched by his burning frustration for Loki's inability to see how he is hurting the ones who love him.
When Fury asks the question, he means to know if Thor is willing to torture his brother, to cause enough pain that answers slide off his silver tongue. Thor is prepared to cause pain. His brother has given him enough grief that Thor might even take pleasure in the first few blows, in twisting Loki's arm behind his back, in pressing his knee where Loki's heart should be and watching pain sneak into his eyes.
Thor forgave his brother for trying to take his throne, for lying about Odin's death, for everything that happened on Asgard except for the end. He does not forgive Loki for letting go. He does not forgive Loki for tricking Thor into believing he was dead. Thor wept for the loss of his brother, for his inability to save Loki, for the betrayal in Loki's eyes as he plummeted into the unknown.
It is not Loki who has been betrayed though. It is Thor. Thor who believed his brother dead only to find him well and plotting. Thor confronted him in on Midgard and demanded him to come home. His brother was alive and that relief, that sweet rush was enough to wash away any of Loki's sins. Thor could forgive Loki for stealing the Tesseract, for causing alarm on Earth, because those could be fixed. Loki could return the artifact, could leave Earth, could come home and Thor would make everything all right.
He likes to believe that Loki would've come home if Iron Man hadn't interrupted their talk.
Thor sees Loki stepping out of the cage, and he reacts. He reacts not to his brother escaping his prison but to his brother preparing to leave, again. Thor knew the cage could not hold his brother if he truly wanted to leave, but watching him stride through those doors was too much. He could not watch Loki leave him again. He knows there are only so many opportunities he will have to save his brother.
This time, it is Thor who falls. He watches Loki's finger hover over the button, and Thor's gut tightens. His eyes plead with Loki not to do this, even as he knows Loki has no other choice. Thor will always offer a way out and Loki will never take it.
He presses the button and Thor begins to fall. He is determined not to die, though. He is determined that one way or another he will rescue Loki and he cannot do that if he is dead. He ignores the fact that this is now the second time Loki has tried to kill him and focuses on what's important, getting out of the Hulk cage.
He smashes through the glass and skitters across the grass. It is a humiliating fall, but there is no one around to see so he forgives Loki that as well. His body aches, but he stands and makes his way over to his hammer. He has fallen quite a distance, and he is far from his allies. He hopes Loki does not kill them.
And yet.
A little bit of him hopes that he does. If Loki kills all who could oppose him, all who know of his existence, then perhaps Thor can bring him home without consequence. The humans will come up with an excuse for what has happened, and if the Avengers are dead then there will be no one to hunt Loki down when Thor brings him back to Asgard. Because Thor will bring him back.
Thor stands beside his hammer and calls it to him. It does not budge. Mjolnir is judging him for placing Loki above the Avengers. Or maybe for being a sentimental fool. How many times does Loki have to try and kill him before Thor will give up?
The answer, as it turns out, is three.
They are on top of the Stark Tower, and Thor grabs his brother's face, demanding, pleading, begging one last time for Loki to give up on his scheme, to come home. Thor's hands dig into Loki's face, harsh, but they are a promise to forgive, a promise to accept, a promise that Thor can fix everything.
He feels a spark of hope as Loki's eyes soften, reflecting the young boy Thor remembers as his brother, and then Loki's lips curl in disdain as he stabs Thor. Thor chokes and takes a step back. This is not what is supposed to happen. Loki is supposed to say yes.
Loki will never say yes.
Thor finally realizes it as Loki throws himself off the Tower. He will always say no. He will always let go. He will always distance himself from Thor, convinced that he can handle it on his own, only to fall deeper and deeper.
Thor reaches out and grabs Loki's ankle before he can disappear again. He hauls his brother back onto the platform as Loki kicks and flails, trying to escape.
"I will not let you go this time," Thor says and his voice has a sharp edge not even Thor recognizes. He grabs Loki's face again, trapping it between his large hands, squeezing until Loki gasps.
Thor drops his forehead to his brother's, thick tears falling from his eyes, christening Loki's face. Thor's fingers tremble at his brother's temples.
"I have always loved you," Thor says, his voice choked with emotion. Rage, humiliation, worry, regret, and melancholy all fight to win the battle in Thor's head, but they are equally matched.
Loki looks at him, eyes burning with scorn. "You have always been weak."
It is an endless cycle the struggle between brothers. Thor saw a glimpse of it before when Loki tried to throw himself off the roof, and Thor can end it here. He can end Loki's suffering, and sentence himself to a lifetime of it.
Thor grips the leather of Loki's uniform and shakes him. "Tell me you love me, brother."
Loki's lips twist into a cruel smile. "I am not your brother."
Thor roars, lifting Loki off the ground before slamming him back into it. Loki's head jerks and his body spasms, but he chokes out a laugh.
"Yes, hurt me. That will make me love you," he sneers. "You are a fool if you think that I will return home with you."
There are tears and snot running down Thor's face, but he does not wipe at it, because he does not want to take his hands off Loki. A dull ache in his side reminds him that he has been stabbed and the weapon is still sticking out of him, but his discomfort is not important now. All that is important, all that has ever been important, is Loki.
"Why can you not love me?" Thor asks, his voice barely above a whisper. "I never hurt you, brother. How can you despise me so?"
"Love is for children," Loki says.
It brings back more pleasant memories. Thor remembers the two of them running around the castle in capes that were too big, getting all caught up in the fabric and tumbling to the floor in fits of giggles. He remembers the first time they fought, back to back, fending off the men the Allfather had sent to test them. He remembers when they were tree climbing and Loki, too short to reach the branch Thor had standing up had tried to jump to it. His fingers had slipped, but Thor grabbed his hand and pulled him up to sit beside him.
Those children are long gone. Laughter has been replaced with cold, distant silence or bitter angry words. They no longer fight together but against each other, and Loki no longer accepts his help. He would rather let go.
"Children," Thor echoes, yanking the blade out of his side. His eyes don't leave his brother's as he plunges the weapon into Loki's chest.
Loki's body jerks on impact, his eyes go wide and his mouth parts as if he had not expected this. But then he sighs, his final breath, and his body relaxes as if this is what he had been waiting for all along.
His eyes have lost their sharp edge, and for a moment he looks lost like the little boy Thor used to know. He reaches up and shuts his brother's eyes, but his hand lingers on Loki's face, cupping his cheek until the warmth drains out of his body.