[BrianG]

Take any BL motor, short all three phases (unhook the ESC first). Feel the resistance as you turn it manually. That's the max brake effect you'll get with the motor (unless the ESC applies reverse voltage to the motor to brake). The faster it is spinning the more braking force is generated. Going really really slow, the motor hardly brakes, but then again, unless you're crawling or on a steep incline, it hardly matters IMO.