I'm going to break things off with a girl causing bad stuff for her
What bad things will happen to her?
She has moved here for me so she will be homeless, she is also pregnant with my baby, so she will have to raise him alone.
That sounds cruel. You're allowed to break up with someone, but you shouldn't do it to make their life worse or without consideration for their suffering.
I am already the bad guy to her, so why should I care?
It sounds like you want to get revenge. If your relationship is toxic, you should end it in the most respectful way possible. You shouldn't deliberately try to cause harm to another person.