Dealing with defense in BESM

In BESM, it seems to be a lot easier to build a character capable of dealing massive amounts of damage than a character capable of taking massive amounts of damage. As a DM, I don’t want to build every possible opponent with massive armor and defense attributes, because it feels unrealistic that everyone walks around in power armor or whatever. What am I meant to be doing to help balance combat? Or is this not meant to be an issue?

The game I’m running is fairly low on combat, mostly social interaction, but when a PC can one-shot just about anyone with a 26-point weapon, they’re getting a little cocky. It’s themed around high-school aged characters, like one of those shows that alternates between slice-of-life filler episodes and battles with season-long reoccurring villains. A lot of their fights are the result of social interaction going badly rather than storming the castle, so I’m not always sure in advance who they’ll pick a fight with.

(We’re in 3rd edition Tri-stat, not d20)