Learn from all your bad relationships. As much as the good relationships define who you should keep. The bad ones define for you your no go areas.
In particular I found work ethic was big for me.
If they didn’t have a work ethic at all “why are you still working” it was a constant annoyance.
Another big one that bugs me is people who don’t see their reliance on other people and think they do everything themselves. Nobody does that …ever.