Clint Barton was loyal. Not to Fury or to S.H.E.I.L.D. Clint Barton was loyal to those who were trustworthy and who trusted him. He was, therefore, completely loyal to Steve Rogers, more commonly known as Captain America. The loyalty wasn't there the first time they met, however much Clint respected Steve. It took a lot to win Clint's respect, and Steve had it from the moment they covered him in history class. Steve was a hero. But Clint respected a lot of people: he respected Bruce's brain, Natasha's fighting skills, and Fury. Steve, perhaps more than the other Avengers (excluding Natasha), trusted him after he blew up half the Helicarrier. Steve, more than the others, knew what it was like to have someone's back—after all, he had been in the Army. But still, Clint didn't trust Steve. Sure, he knew that Steve would give his life for him; he knew that Steve would never give up secrets, even under torture. And he knew that Steve would never do anything to put him in danger, but he still didn't trust him. He only trusted one person, and that was himself; he had been hurt too much in the past to ever trust anyone. He knew Steve trusted him, but he also knew that Steve trusted too easily, and so he never thought he would trust Steve.
So when, while fighting a thing from outer space, they were separated from the rest of the team and captured and hauled out to some distant star (sadly, this wasn't really that uncommon), Clint didn't have complete faith that Steve would get them out. The aliens were big green lizards, right out of the cartoons, and the head honcho was even bigger and greener than the rest. Clint and Steve were dragged, bound in some sort of extra-terrestrial duct tape to the room that Clint dubbed the throne room, due to the large light bulb shaped structure that the head lizard lay on while his subordinates crawled around the floor. Steve and Clint both knew that there was little chance of rescue, since their resident alien was dealing with some sort of trouble in Asgard. But Clint had never relied on anyone to rescue him.
The alien king—Bob, Clint called him, since he looked like a Bob—picked Steve out pretty easily as the leader, since Steve was a lot taller than Clint and looked more … leaderish. It didn't take long for Bob to tell them how doomed they were: "You will never escape me . . ."
Normally Clint at this point would have made some sarcastic comment, most likely about the guy's lizard breath, but Steve stepped forward and did his diplomat thing. "Listen, sir, I think this little misunderstanding can be cleared up . . .", but he didn't get far before he was knocked over the head by one of the goons standing behind them. Steve dropped like a sack of potatoes: Clint didn't really think much of Cap's negotiating skills.
Bob slithered down from his lamp to crouch before them, his glowing yellow eyes winking in what may have been glee, but Clint wasn't an expert on lizard expressions. Steve was already struggling up, making Clint once again jealous of the super serum. The lizard king spoke, his voice unlike what one would expect from a lizard, deep and powerful—even, if Clint dared say, calming and honest sounding. Clint distrusted him even more. "My dear captain, I've heard so much about you."
Clint was about to zone out: all the super villains they fought seemed to think they were original; maybe it was part of the thing that made them want to take over the world. Instead he was thinking of their escape. First of all they had come in through a machine that Clint could not make heads or tails of. Then there were the couple dozen guards, each holding a spear like thing with two ends, one fired stuns, as they had seen, and another killed, reminding Clint of the phasers on star trek. They could make an escape if they got one of the weapons and could operate the machine, but it would be difficult.
"Look," said Bob, "I know that you are Captain America. That you are a soldier out of time. That you had friends. You know as well as I do that your new friends do not measure up to the standards of your old ones. Look at little Hawkeye here. He is an assassin, sent to kill people. He's killed innocents. He even killed the people he worked with. He blew up your ship, putting your life in danger. I will give you a chance. You can go back to your time, create an alternate timeline. See Peggy. Howard. Have children. I'll even send you back with enough time to save Bucky. You will be able to live what you have been dreaming of since the second you woke up."
Clint could see the longing in Steve's eyes. The pure desire. The feeling that if he didn't take this chance, he had nothing to live for.
"What's the catch?" Steve asked, voice hoarse with hundreds of emotions.
"It requires a human sacrifice: your friend the Hawk must die."
Clint would not look at Steve. He knew what Steve's choice would be. Even if it was just a chance. A silver of a chance. Had he been in Steve's place, Clint would have killed anyone to take it. Clint was not a good person. Not by Captain Americas standards. And maybe not even by his own.
Clint finally looked up at Steve, who had been handed a phaser-thing, the kill end aimed at Clint's head. Clint tried to convey that he did not mind death. That it was okay. Steve looked back at him, his eyes filled with resolve and longing.
And Steve spun the rod, firing at the lead lizard who fell, his eyes filled with shock and fury. Clint, his body reacting as it had been trained, though his mind was still years behind, leaped up, easily twisting the phaser-rod from the lizard standing nearest to him while his legs twisted around its neck and snapped it. And together Clint and Steve fought, dodging blasts of light and destroying those who stood in their way. They fought until they reached the entrance hall where Steve twisted a few dials on the machine that transported them there. "Photographic memory," he said with a faint smile when Clint gave him a quick, questioning glance.
And then they leaped through, landing in what seemed to be an empty field in Kansas. They helped each other up, both bleeding and wounded, and made to the nearest farmhouse, which they could both see in the far distance. "Thanks," said Clint, not knowing what else to say, and hoping Steve wouldn't hate him.
Steve smiled, "I just keep you around for your wonderful cooking."
Clint Barton didn't respect a lot of people and he didn't trust easily. But he did respect Captain America and he did trust one person: Steve Rogers. And from these stemmed a loyalty that not even Thor's mighty hammer could break.