There can’t be a full list of secrets without cheating secrets. Cheating and infidelity are some of the worst kind of secrets. Infidelity is all about deceiving the one you supposedly love. Who would want to intentionally hurt someone they love? Maybe you should ask a cheater what their mindset is around their decision-making.
This person describes how their parents met. They met while the mother was still married to her first husband. “My mother PURSUED my father while she was married. My father MOVED IN with my mother and her husband-at-the-time for a couple months before the husband moved out. Poor guy.”