This probably would help.
Aggressive people are related to more than their fair share of my social headaches.
Normal people and I might have misunderstandings, but I think it makes a big difference that we're both at least trying.
A lot of aggression comes from a bad place. It might be manipulative, it might be due to specific internal issues with objective causes, and there are several forms of "internal chaos" that do it.
Most such people present as bullies sometimes.
The point being everyone meets such people now and then. It's a good idea to figure out (or learn) ways to minimize the harm they do, disengage, and to discourage them from interacting again.
FYI "Assertiveness Training" doesn't (or didn't when I was more familiar with it) exactly teach how to deal with troublesome people. It teaches students to be able to react accurately in situations where you're tempted to "let it go", "not rock the boat", or avoid discomfort.
"React accurately" is essentially "assess the situation; decide how to act, even if it's potentially uncomfortable; execute your plan".
Which sounds easy, but you need practice and confidence in your ability to execute your plan.
Apparently classroom scenarios with real people (e.g. role-play with instructors, teaching aides, and/or fellow students) are reasonably effective for that.
The possibility of "subversion" of such education is real these days though.
I've seen people using assertiveness techniques on YouTube quite often of late: it's predominantly one side of the "Culture War" using low-level techniques, and implementing them poorly.
That's a sign of brief training sessions (like part of a weekend "boot camp") designed for people who feel they're in a conflict, and (let's say) are low-level people / foot-soldiers. Which is why (a) they use very basic techniques, and (b) they still get them wrong, and/or fail in the face of equally simple resistance.
I don't believe something like that would be helpful for you.
The point of this is that I think you should be selective about where you look for this kind of training. Something done by e.g. a serious psychologist (individual or organization) aimed at normal people who are avoidant, shy, or easily stressed by unfamiliar situations.
That should serve to create a foundation. Then you'll know what you can and can't actually do IRL when faced with a psycho. Which in turn means you can select techniques that will probably work for you.
Mistakes and imperfections are still inevitable OFC, but fewer is better
