I'm sorry Witz. Sadly, this sounds all too familiar to me. Oldest has walked out on many a lease, even has judgments against her for past rent due. She leaves things behind, including a big mess. She used to check herself in to the psychiatric unit whenever things got too bad, as a way of escape, and also as a way of seeking sympathy from those who were angry at her, in my opinion. It was incredibly manipulative. No, I don't think that makes your difficult child (or Oldest) a sociopath. In Oldest's case, I think it's a severe manifestation of her borderline personality disorder, this inability to accept any responsibility for her actions, or to clean up her messes, or accept criticism, even if well-intended (I need to speak to her again about her hygiene, she's showed up at my office a few times recently reeking of stale cigarettes and b.o., it's embarrassing). Everything is someone else's fault. There is no remorse when things go wrong, only excuses. Although recently, Oldest has taken to blaming herself when things take a bad turn, saying things like "I can't do anything right" ... honestly, another manipulative tactic, in my book.
It's a heck of a way to live.