What red flag about your ex do you wish you had paid more attention to?

We are SO good at ignoring the bad signs, aren't we? Even when the red flags are literally waving in our faces.

What's one red flag that you wish you would have paid attention to more in retrospect?

Two for me:

1) My ex's own FRIEND told me I shouldn't date him, and, yet, date him I did.

2) Also, he was super protective of his phone — I'm not a snooper, but if i so much as touched it (to, like, look at the time if his phone were closer to me than my phone), he would yank it away from me. Definitely not the actions of someone with something to hide. Not at all.

How about you? What red flags did you ignore?