Have you ever given someone a chance and then regretted it?

I'm 35 and I used to work in a health food store. A while back, I ran into a former customer of mine from the store and he asked me for my phone number. The guy was 51 and had white (not gray) hair and wrinkles. I wasn't really attracted to him, but he seemed nice, so I gave him a chance. Well, I now regret having given him that chance. We dated for 3 months, and I learned during those 3 months that he is an egotistical, self-centered, weak cad! I ended up dumping him after he was inconsiderate towards me for the umpteenth time. Have you ever given someone you weren't attracted to a chance, and then ended up regretting it? If so, tell me your story.