The soldier the government picked to be the next Captain America, who was qualified on paper in every way that turned out not to matter.
John Walker is the series arguing with itself. On paper he is the correct choice: three Medals of Honor, a decorated captain in the 75th Ranger Regiment, tested at MIT and above average in everything. What he does not have is the thing Steve Rogers had, and the show is honest enough to admit that nobody can say precisely what that was.
Wyatt Russell plays him as a man who can feel the gap and cannot name it. Then his partner Lemar Hoskins is killed in front of him, and he kills a man with the shield in a public square in daylight, and the series has its image.