I just read a couple of stories by charmingcontender (A Flaw in my Code and Arsonist's Lullaby at AO3) where Steve is fiercely protective of Bucky. With some clandestine help from the team he breaks Bucky out of custody and treatens anyone who gets in their way when he realizes the Winter Soldier trial is a mockery and no matter what he says Bucky's already tried and convicted. In one story the Asset's former student, Widow, joins them in taking out those who had a hand in abusing Bucky while he was the Soldier. Captain America shows a ferocity and bloodthirstyness I've never seen anyone else ever write for him and I'd love to know if there are any other stories out there that show such a dark side to usually goody-two-shoes Steve Rogers.
I'm not talking about ABO stories where he mates Tony by force or anything like that. I'm looking for ones where the really dark side of him comes out in protection of what's his, be it Bucky, a lover, or the team.