If I understand your question correctly, you want to know about how to end the relationship with your ex. As you said, you probably already know the answer to this question. One possible tactical error in the relationship was taking the blame for incidents that were not your fault. The potential drawback that such a move may have had was to reinforce the very behavior that you found to be problematic. Your taking the blame could have given her the impression that she can engage in unacceptable behavior without penalty. It may also have led her to believe that she maintains some level of control over you and the relationship.
I only have your version of events. To give you the best possible advice, I would need both sides of the story. Given the information that I was provided and your stated desire to end the relationship, the best course of action would be to stop all contact with her. All contact is the operative phrase. Any contact, even a short e-mail or a text message, etc. could send the message that you still want her in your life.
If you’re having difficulty knowing how to proceed, you may want to consult a therapist. Ending this relationship may not be a straightforward process. A therapist could provide the necessary relationship guidance that you may need in this situation. I wish you the best. Please take care.