Now we have the final section, the people I spotted in more than one film, but unfortunately was unable to name confidently, often there was just nothing to work with.

Unknown Foreign Actor (1) [possible name Jim Norris] --- NEW to HKMDB
https://hkmdb.com/db/people/view.mhtml?id=137883&display_set=eng

Secret Executioners [1982]
https://hkmdb.com/db/movies/view.mhtml?id=10062&display_set=eng


Mission Thunderbolt [1983]
https://hkmdb.com/db/movies/view.mhtml?id=15189&display_set=eng


Struggle For Leader [1983]
https://hkmdb.com/db/movies/view.mhtml?display_set=eng&id=6470


Ninja, Phantom Heros U.S.A. [1987]
https://hkmdb.com/db/movies/view.mhtml?id=15929&display_set=eng

A possible match.
Unfortunately, I can't remember the name of the movie.
It features a character who swears, early in the film, "Vincent, I must revenge ON him".
The film was released late in 1991.
It featured Vietnamese refugees.
I found the film here a few years ago, but cannot remember the name. Damn.

This guy, if he is a match, was of course a gwailo villain, one terrific kicker and badass,
who played an obnoxious American who liked to sit with his feet plonked on a desk.

Sounds interesting, but unfortunately I doubt it's the same guy, as you describe him as "one terrific kicker and badess", whereas if you watch this guy's action in Secret Executioners you will conclude that he is neither

But I'll keep an eye out.
Cheers