Tear Jerker / Infinite Coffee and Protection Detail

• Steve and Tony's five-day fight and the argument that caused Tony to snap. Tony is rightly furious at who he perceived to be his parents' murderer and is within his rights not to allow Bucky in Avengers Tower. Steve laying out the gist of Bucky's trauma for the last 70 years and digging up Tony's own checkered past still hurts.
  Tony: Everyone has a choice.
  Steve: You think that? You think he has a choice about being frozen for years on end? You think he had a choice about that arm? He didn't even know me, Stark. What are the chances that he had any idea what he was doing for HYDRA except what he was told? What do you think they did to him when he didn't do what he was told?
  Tony: He killed. My parents. And how many other people?
  Steve: Not nearly as many as you killed with Stark weapons.
  Tony: Get Out!
• The horrifying scene where the HYDRA operatives break in to try and reclaim the Asset. After no-selling HYDRA codewords for so long, Mission Imperative finally gives out. It's heartbreaking to see the same Mission that, throughout the fic, desperately tries to make contact with Steve and protect him, shriek at Barnes to kill Steve. Barnes struggles against the orders, refusing to kill Steve: messy-haired, wet-eyed, wearing sheep pants, and ready to die. Even with a pistol pointed at him, Steve refuses to fight Bucky.
• After the situation with the HYDRA handler is resolved, Mission Imperative is hurt, confused, and angry. It goes silent for a long time and doesn't turn up until the sequel (granted, in a Big Damn Heroes moment).
• Barnes and Steve’s mutual anguish after Barnes accidentally nearly punched Steve’s eye out, having dissociated thanks to the sparring gear an oblivious Steve coaxed him into wearing and thinking Steve is a HYDRA handler he needs to defend himself against. Barnes punishes himself by locking himself up in his closet, and when Natasha comes to check on him he thinks she’s arrived to execute him for his failure. Steve is stricken and feels horribly guilty for what he accidentally put Barnes through.