When you encounter those nasty controllers, solid buildings are your best friend (this is because their psi attacks get disrupted by physical barriers). Finding a good spot inside a structure with thick walls gives you much better chances than being caught in the open, where their mental attacks hit hardest. You'll notice they usually bring zombie friends along, which is actually important to deal with first, since fighting both at once can quickly become overwhelming.

Something interesting to know: psi protection pills are incredibly valuable here, because they reduce how badly those hallucinations mess with your head (keep a few in your quick-access slots). The most effective approach I've found is working from decent cover with an assault rifle or shotgun, then making calculated pushes when the controller's attack pattern gives you an opening. This works because controllers actually struggle with targets that close the distance quickly.

If you're caught outside without proper cover, don't panic - your best bet is actually to rush them down with a shotgun (sounds counter-intuitive, but mid-range is where they're most dangerous). Always make sure you have an escape route planned, though, because their patrols can sometimes circle around to flank you when you least expect it. Remember, those mental attacks might feel overwhelming at first, but with proper positioning and timing, you can definitely handle them.