I saw the start of a film awhile back but can not remember the name.
It started in the states maybe n the seventies where a family were having a party around a pool. Two people arrive and the woman recognizes one of the guests as a former nazi. The former nazi then takes out a gun and shoots most of the guests. This was as far as I got through the film. Any ideas on the title?

Not a film, its a series. Hunters

https://en.wikipedia.org/wiki/Hunters_(2020_TV_series)

Many thanks, will watch the rest of it now!