I've talked a lot about ways to prepare and build characters. I think I've revised and redefined my 'quick templates' for making NPCs - important or otherwise - several times this year. Most recently focusing on the character's 'Core Need' versus their 'Want' and with antagonists/allies going so far as to break down their 'Grand Goal' and 'Current Scheme.'
Recently though I came across a term for another facet of a character that I think is important - especially for major antagonists and allies. That term, or aspet, is their 'Pathological Maneuver.'
What Is It?
Novelist Elizabeth George defines a character's pathological maneuver as how they react when under stress - in particular when they are denied their core need. The in particular is because the denial of a core need is what puts us under stress in the first place, but anything that makes our goals harder to achieve will cause some stress.
In other words, the Pathological Maneuver is how the character reacts to adverse conditions and failure to meet their goals. This is good to know, and have defined, because it tells a lot about the character. As the saying goes, speak with a man every day for 50 years and at the end hold him over a volcano's edge. On that last day you will finally meet the man.
How we react to stress does a lot to define us. Do we turn inward and self blame? Do we become cold, ruthless, and efficient? Do we lash out? Do we point the finger and put the blame on others? Do we twist facts to make ourselves into the victim?
How is it Useful As A GM?
Knowing the Pathological Maneuver for important NPCs will let you play them better, sell them as real people better, and react more naturally. A villain with a victim complex will play and feel a lot different than a villain that gets brutally efficient, even when everything else about the villains is the same.
This applies to allies as well. A stressed ally provides interesting new obstacles for PCs, and how the ally acts when stressed can change how that works out.
Most useful though is in the moment when the PCs thwart plans. Having a guide for how the villain reacts can make a scene so much more memorable because there isn't that pause as your brain tries to catch up with the unexpected thing that just happened.
How Is It Useful As A Player?
If you're trying to differentiate a character from yourself, or another character, how they react when denied is a big thing to change. When we're challenged we see how a character really is. This is also where most of the murder hobo stories come from. PCs are challenged, so they respond with violence.
However, mixing up how your characters react when denied builds in variety to the character. Having it written down somewhere you can reference also helps stop your pathological maneuver from cutting in for the character. Which in turn can help keep you grounded in the character, and avoid blurring In Character emotions with your Out of Character ones.