I am lucky that all my relationships (I started dating very late and haven't had many) have ended relatively amicably and I remain on good terms with them. My relationship before my current one we just had different future goals (I am childfree, she is not) so decided to end things with no hard feelings.

I wouldn't say I am still close to any of them, but I haven't blacklisted them and it isn't awkward at all if a social situation involving both of us comes up. I have never had a "bad breakup" though, so that would probably be a fair bit different.