Frank Castle's oldest friend from the service, who found out war paid better as a business than as a duty.
Billy Russo is Frank Castle’s former best friend from their time together in Force Recon, and he runs Anvil, a private military corporation. Ben Barnes plays him as the man Frank could have become if he had been willing to sell the thing they both did overseas, and the first season works because it takes its time before making you choose which one of them is right.
The second season is where the comics catch up. Russo develops scars on his face, memory loss and, as the series puts it, a mind broken like a jigsaw puzzle, after Castle bashes his head into a mirror at the end of the first season. That is where the name comes from.
Show detailsThe name is never said
Wikipedia lists him as Billy Russo / Jigsaw and the second season builds the scars, the mask and the psychiatrist around exactly that idea. The show itself is more reluctant with the name than the comics are, which is true of most of the Netflix run.