It could be a lot of things - Narcissism certainly, but defensiveness as a response to criticism is also pretty common in folks with ADHD due to what we experience in the educational system… I’ve had to train myself to be more open to criticism but any criticism in the realm of laziness still makes me quite defensive.

The “No one understands you just me” is classic predatory behavior that’s often accompanied by trying to isolate you from your family, again, it could come from narcissism but it’s also frequently tied to plain old insecurity but in an extreme form.

It sounds like you’re happy getting out of that relationship - whatever is wrong with them is their fucking problem and not yours. One of the hardest part about ending an emotionally abusive relationship is removing them from your day to day thoughts - so it might not be healthy to dwell on them even in this form, it might help to understand the damage better and find like folks but it’s also important to close that door.