The Aftermath (1982)

 

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Two astronauts return to earth ("a few miles off the coast of Los Angeles") to find that it has been destroyed by nuclear war. L.A. has been taken over by Cutter and his gang of outlaw bikers (straight out of the 70s with bell bottoms and everything). Cutter rapes and pillages. Of course, there are also mutants. The astronauts hook-up with the only normal people left: two good-looking women, and two cute little children; a boy and a girl.