Leaving Asgard was both a blessing and a curse to Loki. He has dealt with giant beasts, dragons, and even his idiot of a brother and even more idiotic friends, but this takes the cake…
When Loki decides to leave Asgard, it is due to being overlooked entirely. Asgard ignored everything he did in a battle because he fought with small blades and daggers and used his magic. So those were seen as cowardly and "unmanly" that Loki wanted to spit the nasty words like the snake he used to be and tell them, 'Odin uses magic. Are you trying to say your king isn't "manly"'? But he refrained. Why? Because it would only result in punishment for him. His words twisted and mangled to make it seem like he was saying his king and father weren't manly to "make himself feel better about using cowardly tricks."
Now, though? Now, Loki doesn't have them around him. He doesn't live in someone's shadow. He is his person. Or so that's what he always tells himself to keep sane and not end his life.
Once he got to Midgard - because Odin would never even think to look there for his second son - he was eventually kidnapped by a group known as HYDRA. Something he consistently hates about them, minus the obvious, is that their symbol isn't even a hydra, yet their saying, "cut off one head, two more grow back," is accurate to the actual creature. A hydra has five heads, not legs, and they sure as Hel aren't tentacles! Moronic people!
Anyway, they figured out that I wouldn't be helpful to them as much as I'd be beneficial to their sister ally, the Red Room. Unfortunately, since the Red Room usually only trains girls from 2-3 years old, and I'm neither young by either Midgard or Asgard terms nor am I a female, they trained me a little differently. Instead of learning to seduce men and men only, they taught me to seduce both men and women and manipulate both, as they called it, "that pretty face and body of yours." They make me sick.
Loki is in a SHIELD interrogation room; he is telling them everything.
"The real problem was I refused to show my seidr," he says, holding up his hand to show them a small ball of green energy rolling around in his palm. An agent by the door has their hand on their gun, unsure if this person in front of them is currently a threat to their boss, Director Nickolas J. Fury. As soon as the ball appeared, it disappeared. "They'd have used it and me to hurt the girls more than they already were doing to them." Loki finishes with a sad lilt to his voice.
Fury narrows his eyes at Loki. "So, why come here when Agent Barton asked you?"
Loki looks at Agent Barton, who is on the left of Director Fury. "Because he realized I didn't want to do what they made me. He knew because he was like me, someone who wasn't allowed a choice in becoming a killer." Agent Barton stands a bit straighter; however, he doesn't seem uncomfortable with that revealed. It's also as if he thought Loki would give out everything about his past in the circus, his brother, his parents, his mentor, and everything. But Loki knows what it's like to have people know your deepest darkest secrets out in the open as if you were a book that changes languages based on who's reading it.
Fury scoffs, "Yeah? And how am I supposed to believe that?"
"By giving me a chance, I'll stay wherever you'd like me to, do whatever you tell me. I want a chance to do good, be good, for once in my life." Loki's voice shows his desperation as clear as day, his face not showing any emotion. That is, except for his eyes. Those tell everything they need to know.
This man won't betray them. This man wants to help them, to help Agent Barton. So fury thought, 'I'll let him be Agent Bartons' partner and have Agent Coulson be his handler. If anything, this would do him a lot of good.'