The concept of original sin. Teach small children they are inherently broken, then weaponize inevitable misbehavior as a sign of their “sinfulness” so they habitually internalize shame, have no self-worth, and as adults become ideal relationship fodder for abusive narcissists. (source)

Many Christians don’t realize/acknowledge the doctrine of original sin isn’t universally accepted across all of Christianity.

Even if you believe, you don’t have to teach your kids this (and punish them for it).