I very (very!) vaguely recall watching this movie a long time ago.
From what I remember there was a former US astronaut who had psychological problems (at one point he explains why he’s afraid to go back into space) and for reasons lost to me he gets involved in a barfight with a gang of bikers. He beats them but is fatally stabbed in the process.
For some reason that scene popped into my head today and I’ve been trying to recall were I saw it.
I thought it was called ‘The Seventh Configuration’ but a google search doesn’t bring anything relevant back for that title or titles like it.
Thanks!
edited to add I think it was a 1970’s movie.