I don't know how many people read the Isis Papers and related work, but it's author mentions how they would mentally break the slaves. I.e. 'look through your slaves for the strongest male slave, the one that clearly has a leadership role in the group, hot tar and beat him to death in front all the slave for all of them to see' or 'hang a pregnant woman upside down, cut her stomach open and allow the fetus to fall to the ground, then stomp the fetus to death in front of all the slaves'
They would make example of slaves for no reason just so the other slaves would know not to try shyt. Occasionally there would b a slave too real to be controlled, like one of the GOATs, Nat Turner
White folk with slaves did live in fear their slaves would killed them, Martha Washington let all her slave free after George died, because she was afraid of just that.