Scenario 1: Punisher. He seems to be better with tactics and certainly knows the urban world better
Scenario 2: We know next to nothing about Franks military service in the movie, so this is unanswerable. In the Ennis story "Born", Frank was the sole survivor of one of the most brutal battles in the Vietnam war, so that would even the odds a little.
Castle doesn't stand any kind of chance in scenario 2.
I think the Punisher owns Rambo in scenario 1. Rambo is completely unfamiliar with cities. He would probably be a bit disoriented as well. He has spent the majority of his life living in seclusion far away from an urban environment. He would probably have another nervous breakdown if he were to visit civilization. The Pun will just camp out on a building and wait for a clean shot.
rambo is too strong, fast and accurate for punisher
rambo would easily dodge his bullets and proceed to blitz and rip his neck off with his hands 😐
you doesn't need to be a world class fighter or marksman to notice that rambo is a FAR better marksman and faster fighter than punisher 😐
rambo rips his throat off