Sci-fi series about an intersteller agent dealing with hot spots or troubles

I’m trying to identify what I believe is a book series from around the 70’s or 80’s but unfortunately, I don’t recall a lot of detail about the author or series. The primary protagnist was a male acting as more or less independent agent who was the brains of the outfit and who was accompanied by a larger, much stronger sidekick (who was either from a primitive world or for some other reason wasn’t too bright); not sure if there was anyone else in the team.

I remember vividly one scene however; the duo have been captured by the story’s (and potentially the series’?) antagonist and are incarcerated onboard a starship. They are then shown a video by the antagonist of the story, of a group of people having an idyllic picnic before an argument breaks out and leads to a rapid escalation of violence and the picnickers killing each other with their bare hands. The duo are then informed that this was as a result of a gas that greatly increases aggression and the event was part of an experiment to test its effectiveness. They are gloatingly informed that the same gas will be introduced to their cell so that they’ll kill each other. When the gas starts to take effect the brains manages to direct the brawn’s induced anger towards the antagonist. The brawn then rips the bars apart and sets off a rampage.

I seem to remember this novel had an illustration of a star ship hovering over a field or landscape and being a shot at by an energy beam or laser.