If anyone claims to have a bunch of crazy exes, ask yourself what the common denominator is.  Be informed, especially if you have children. Ask yourself, “How does someone get to a place where they have zero friends but me, whom they’ve just met?”
They didn’t know their partner had a secret life
Profile of the Sociopath and the Narcisscist
How to spot a sociopath – 10 red flags
Psychopaths: 30 Red Flags
Beware the narcissist disguised as your soul mate