Not that I've really had that many romantic relationships, but...

1. Refusing to allow me to pursue my interests, or discouraging me from having interests of my own.  Of course, I expect that my partner will have his own interests, and that we will have common interests and activities that we can do together.  Hell, I'd love to have someone to do things *with*!  But don't cling, either. 

2. Passive-aggressive behavior.  Heck, that bugs me from anyone, but especially from a partner.  We *are* both grownups here, aren't we?  Talk to me, don't expect me to read your mind all the time.

3. Not pulling your weight.  I don't care if it's housework, money earning, whatever... I know we each have our strengths and skills, just don't expect me to do it all!  Do what you can to contribute to the relationship and the household.  I can do flexible amounts of work, and we'll take turns, but don't sit on your ass all day while I work and then have to take care of everything else as well.

There are other less important things, but those deal more with individual personality or attractiveness traits. 
No, not bitter....just lacking in positive history.