This movie's a shaggy dog joke. Like all shaggy dog jokes, the joke is mainly on the viewer: how warmly you receive it is based on how funny you think it is when somebody tells you a long joke without a punchline, artfully stringing you along.
Yes: The title character kills Hitler. Yes: The title character eventually kills Bigfoot. Then, the movie shambles onward for another half-hour before unceremoniously dying.
Still, there are some satisfying--even weirdly beautiful--moments along the way. There is a tale of lost (or missed) love; a tale of close brothers that will never truly know each other; a look at the numbness of being a combat veteran; and a very timely discussion about the nature of fascism.
In short: if you are EXTREMELY patient, and really like Sam Elliot, you'll find this rewarding. But it's an indy production, and a very slow burn.