I hated my last job
I printed out lists of account numbers and anonymously sent them to a rival company.
I would steal the passwords of less tech-savvy workmates to help me get away with doing as little work as possible. One temp employee got fired after I used his account to sit around doing nothing, that didn’t stop me doing it though. I was asked to help design a new employee-monitoring system, while designing it the first thing in my mind was making it easy for me to slack off; at the expense of others where neccessary.
Loads of people gave me their contact details before I left, I promised to meet them often. One guy hinted at me being the best man at his wedding, a girl wanted me to go on holiday with her and her friend. I’ve not spoken to any of them since, I even changed my mobile phone number.