I think it's natural to feel bad or guilty but what you have to remember is that in "normal" healthy situations, you don't have to cut off contact. For example, I greatly limit contact with my mother after a long lifetime of her control, criticism, drama, and generally toxic way of interacting with the entire world. Now, society would say "You have to love your mother no matter what!" Well, I do love her, I just don't give her unlimited access to emotionally abuse me. She tries to make me feel guilty but it's so over the top that it doesn't phase me. Sometimes I feel guilty in a more general way but I remind myself that my mother is not a loving, nurturing, healthy individual.

So just try reminding yourself that you had to end the relationship because of how toxic it was. I don't know your specific situation but probably you were not the one making it toxic. It's really out of your control, you can't control another person, only protect yourself when need be. Their actions are their choice.