He has fought valiantly, but his future self is stronger, more ruthless, and more experienced, and he wants Loki to burn like he burns. So he has taken himself, his essence, everything that makes him him, and stuffed it all into Loki’s defenseless mind.
All the bitterness, all the anger that has slowly eroded Loki’s heroic resolve over untold centuries until he became King Loki, Loki is now forced to experience over the course of seconds. No mind can withstand that; his body convulses in the electric chair, once, twice, before he passes out, a rivulet of blood running down from his nose.
But unconsciousness brings no respite. King Loki’s memories rampage through his mind like an out-of-control wildfire, consuming everything in its passage. Loki’s mind feebly cries out for help, knowing full well his future self has made sure no one will come. Not Sigurd and Lorelei, imprisoned through Loki’s own betrayal. Not Verity (I told you, Loki, I can’t do it anymore. I’m done.). Not his father ("Then-- then you must help me--" "No. I must not. The blood must have the fire."). Not his mother, who exiled him, and betrayed him before that. Not the valiant people of Asgard (Who speaks? Surely the empty air! And none here speak to air. None here speak to ghosts.). Not his brother (Never call me that again, lie-smith. Thou art no kin of mine.). No, Loki must face the onslaught alone, and there is nothing he can do against the raging inferno, and so he burns.
The older Loki watches jubilantly as his younger self crumbles. He can follow the path of the devastation with every wince of the unconscious man. There, he knows, goes the wish to atone. There, the hope for acceptance. There, the desire to do good. There, the will to change. There goes the attachment to Midgard, there the fear of his own power, there everything poor little deluded Loki has used to hold himself back from his destiny.
If Loki were the hero of this narrative, then this, the hero’s lowest point, when all seems lost, this would be the point where the deus ex machina would turn things in his favor. Something would happen to interrupt the villain, the hero would get a few seconds to gather his wits, and realize there is indeed a way out, a way to foil the bad guy - by escaping into death if everything else fails.
If this were Loki’s narrative, he could save himself. But King Loki’s magic is strong, and he has had centuries to learn how to impose his narrative on the universe. Loki doesn’t stand a chance. There is no last minute salvation. There is no last minute suicide. There is only King Loki’s memories, burning in Loki’s heart and mind. If our memories make us who we are, then by knowing what King Loki knows, seeing what King Loki has seen, feeling what King Loki has felt - hasn’t Loki just become his own worst enemy?
There can be no last minute salvation because King Loki doesn’t want to be saved. There can be no last minute suicide because King Loki doesn’t want to die. What King Loki wants is to live and to not be alone in his insanity, and so it shall be because Loki is King Loki and King Loki is him. The narrative has decreed it so and they cannot escape the narrative; all they can do is burn and burn and burn.
Eventually the fire dies down to embers, its work done (but it doesn’t die, oh no, it burns inside them forever). The Loki who is tied down, Loki-who-was-the-youth, stirs and lets out a groan muffled by his muzzle. Loki-who-was-the-elder obligingly waves his hand and the offending gag vanishes. He leans close to his other self and croons against the shell of his ear, "Poor little lamb. I know, I know, it hurts. But don’t you feel better now that the bandaid’s been ripped off? Hmm?"
Loki’s cheeks are hot and red and there are tears drying on them and when he speaks, his voice is hoarse and he sounds so, so lost. "I want the world to burn," he moans miserably. "I want to make it burn."
"How fortuitous, then, that I want to make it burn too!" Loki-who-was-king-of-Midgard laughs. "We can make the world burn together." His wrinkled hands caress the other’s bound wrists, slowly travel up his naked arms, over his biceps, as he whispers into the ear of Loki-who-was-the-agent-of-Asgard, "Won’t that be fun? We’ll make a family outing of it! It will be…" His roving hands come to rest tenderly over the leather strap restraining Loki’s neck, "a bonding experience! Haha!"
Loki looks at him balefully, his big green eyes still shining with unshed tears. "I… I just wanted…"
"Yes, yes, yes, you wanted everyone to like you, so you tried to mold yourself into what you thought they wanted. And now you know that was never going to work. I-" he plants an almost motherly kiss on Loki’s brow, "-opened your eyes. Now you know that what you thought they wanted was not what they wanted at all! They wanted Loki. The one you claimed you were nothing like." He points a finger at his chest. "The old snarly one. Well lucky them! Now you know, and they get two Lokis! Exactly what they wanted and more! No such thing as too much of a good thing, right?" Loki’s maniacal laugh fills the room. He laughs and laughs, bent almost in half, for an uncomfortably long time, until finally he wheezes and has to stop, and when he straightens out he turns all his attention back on Loki. "You’re not laughing. Why aren’t you laughing? Aren’t you happy you can give them what they want after all?"
Loki gazes back up at Loki. "I… Yes. I just wish they wanted something else."
Loki sighs. "Oh, Loki. My poor little Loki. You were never going to be a hero with that skeleton in your closet, and they were never going to love you after the truth came out. They never loved you. They could never love you." He leans in close again. "But I do."
Then Loki’s lips meet Loki’s, and Loki sighs and lets him in, and just like that they are kissing. It’s artless and hungry but they both want so much, they are both nothing but instinct. Loki’s hands tangle viciously in Loki’s hair, and Loki groans and bites Loki’s lower lip in retaliation. Loki lets go with his right hand only long enough to flick his wrist, and suddenly the straps tying Loki’s arms to the chair vanish. He uses his newfound freedom to rake his nails down Loki’s back, and Loki sighs in satisfaction. Their heated breath mingles, intoxicating, and soon they are lost in the sensations, and when they come up for air they can’t remember they were ever separate people.
There is a phone lying abandoned in the wreckage of the apartment. It used to belong to one of them, but they can’t remember which. They don’t care. They burn.