What is a relationship deal breaker for you?

I believe that most things can be built up, improved, or even introduced into relationships.
But if the other side is not open to trying, then there may not be much that can be done about some things.

I would hope that the other side would be open to trying things, open to improving and doing new things, open to fixing things in different ways if what we tried hasn't worked, but if in the end the person just isn't open to it, i would feel that it may just not be a right fit for me.

Most things can be worked on, but if one side is not open to working on things in what ever way would help, then there may just not be much to do.

If I cannot trust who ever is in the relationship with me, I will always have a negative feeling that I may one day be badly surprised by something this person has done.

This is true for me for all types of relationships.
If I cannot trust the person in the relationship with me, I will just not be able to feel comfortable with them. I wont be able to comfortably share things with them, talking to them, and being with them.