Ed Brubaker and Steve Epting's Captain America run is one of the all-time greats of the medium, and one whose influence can most palpably be felt in the MCU, where it's inspired all three Captain America films to varying degrees of success.
Brubaker's run was most famed for its resurrection of Bucky Barnes, who was revealed to have survived the blast from WW2 and was subsequently captured by Soviet spies. There, he became the Winter Soldier, a man out of time tasked with assassinating the U.S.S.R.'s political opponents and various other kinds of espionage. Fortunately, it didn't take long for Buck to snap out of his trance and go back to being Steve Roger's best pal, even succeeding his friend as Cap when he passed away in the wake of 2006's Civil War.
It's during that conflict in which Winter Kills is set. During the one-shot, Brubaker places Bucky on a journey that forces him to address his time spent as an assassin head on, while assisting Nick Fury in his attempts to steer the Young Avengers away from a Hyrdra base way above their pay-grade.
There were plenty of stellar issues from Brubaker's run, but the fact that Winter Kills is largely self-contained aides it greatly. Round it all off with some stunning art from Lee Weeks, and you have everything that made Brubaker's comic so appealing condensed into one issue.