Electrocuted
This was one of the favourite tortures of Thanos'. He would put a nice metal clamp in one of Loki's fingers and another one in the opposite foot – and then turn the electricity on. With higher and higher voltages each time, so that he could never get used to it. So that every time would hurt more and more, so that every he would dread it and fear it more and more.
“I'm only making you stronger.” The madman said, “one day, you'll thank me for my help.”
The truth was, Loki was at Thanos' mercy. When he'd arrived in his company he'd been shattered, both mentally and physcially. aAter discovering the truth about himself, trying to fix it and then being rejected by his father as he hung on the edge of an abyss and then deciding to end it all his mind had decided that it reached its limit, its tipping point and couldn't take any longer. All his defenses were destroyed, all his masks and personas. He just had no strength to face anything else.
And physically... well, by the time he'd made it to Thanos' place he'd already been falling and falling and falling throughout the cold vast universe for days and days, no food, no water, no rest, just an ending fall that broke all he was, burned him, hurt his eyes and airways. He'd been so easy to take, and even then he'd been defiant. I work alone, he would say, I don't take anyone's orders – if you need something from Midgard you take it yourself.
And that was when it started, when he started “teaching him lessons”, “making him stronger”. The methods varied, but Thanos found out that while ice and cold nearly had no effect on him, electricity did wonders to bend that little Asgardian's will. Oh, the fun he had watching him squirm and plead not to do it, Thanos hadn't enjoyed himself this much since the times when he used to Gamora and Nebula against each other.
And Loki didn't know what to do, how to escape. His mind was still in pieces after everything that had happened, and all that electricity, all that pain coursing through clouded his head even more. It was difficult to think, it was difficult to breathe, it was difficult to do anything other than scream, and scream, and scream. And he could harldy stand, which made any attempt to escape exceedingly difficult.
But he had no allies, no one he could convince into helping him. Apart from Thanos there was only occasionally the other, who would help him in the end, Loki was sure, but needed to think he was not helping – getting him away from Thanos was too obvious, he needed something more subtle. But Loki was beginning to think that there was no time for subtleties. That this was it.
He didn't mind all that much. Sure, he would have preferred to die by his own hand, by his own choice and not due to the tortures of a madman, but at least he would stop hurting. There would be no more shocks, no more burnt skin and flesh on his hands and wrists and feet. He wouldn't have to endure any more speeches, any more of Thanos' big words for anything. So Loki just the man do his worst, and hoped that his end would come soon.
Thanos' kept at it. He would change the voltage of the electricity mid-shock, so that the body couldn't get used to anything. So that Loki would think that the day's session was ending, when it still had so much more to go on. Loki hardly even screamed anymore, trading his cries for smaller whimpers and silent tears. He had given up.
Thanos didn't like that, and tried varying his punishments to get a better reaction, but nothing. Loki just took it, and Thanos hated that. He didn't want that complacency, he wanted suffering and horror and pleading eyes telling him to stop, that he would do anything for it to stop. That was why he did all of this.
So the madman left to think about some new better, improved punishment and Loki had time to gather his thoughts, despite the smell of burned flesh (his own flesh) assaulting his senses. There was a chance.... If he played his cards.... He could go to Midgard, and pretend he was doing what Thanos was doing. Hell, he could try and take it for himself, if it was so mighty. And then... when he eventually lost (he really hadn't the motivation enough to win this, and he knew it)... maybe they would take him to Asgard for trial.
He would see his mother... She may have lied to him his whole life, but was still a better sight than... this. And he didn't know how much longer he had to live, but he knew that this was not the last thing he wanted to see. A purple man with airs of grandeur, no, he deserved better than this. He deserved to go home once before dying, he deserved, seeing his brother again, a small chance of making things right. And he could get it, if he went to Midgard and lost.
And lose he would.
When Thanos came back with some electrified chains, Loki put together his broken down hands and started the charade. Please, no more electricity, I'll go, I'll obey you, I'll be your spy on Midgard, I'll never tell on you, I'll do anything. He was glad he was such a good actor. In fact, he decided that the story he would tell on Asgard would be that he chose to go to Midgard, maybe as a revenge against Thor? Yes, that was a good story, better than the actual one.
And so he went to Midgard, and lost, and tried to forget.
All the memories came rushing down when Thor put one of those disks on him on Sakaar. He was suddenly frozen in the spot, dread eating him whole, even if the disks were smaller, even if the potency was a tiny part of what Thanos had put him through. But the horror of finding himself trapped in there, again, in the mercy of those damned electrical currents...
Luckily, it didn't last long. When Korg and his associates helped him up Loki felt.... much better. This time he was able to defeat the electricity without begging, this time his mind was whole enough to convince this guys to help him, and help Asgard too. This time...
This time he won. And no one could take that victory away from him.