Often in novels and television shows, it can seem like fights start for no reason at all. The author bases their fights around a moral stand point, the other character is a bully, they are a bad person, or evil, and there are often no follow up consequences.
It’s actually rare in life to find a living person who wanders around randomly spoiling for a fight. Now, they do exist, I know people who’ve met a few, but the amount that they actually appear in fiction is actually rather ridiculous.
Someone who’s planning to start a fight will actively assess several different factors. Here are some basic ones:
-They will weigh their chance of injury and death versus success
-They will look at the numbers advantage (does their opponent have more people than they do)
-What is the target’s social connections
-What fallout will occur with victory and defeat
-What they can gain from the fight versus what they will lose
-The cost of victory
Even if your villain is a minor character, spend some time with them, and examine what their motivation is. The same is true for your hero. Most victories are won in combat without ever firing a shot and someone trained and untrained will notice (sometimes subconsciously) the difference between a character who is pretending they know how to fuck someone up and a character who really does.
What one character knows about another will change the underlying reasons for why they are fighting and remember, no fight is free. There are always consequences.