Let a narcisist bipolar family member onto my home server for phaseI. For phaseII I granted too much access in sudo because I was busy. Fast forward a year or two and a downswing triggers the victim rage and he attempts to wreck my server after a minor argument -- would have, too, if I wasn't keenly aware of a conversation he had a few weeks before where he detailed "how to fuck with someone horribly" to a peer and I used that recollection to reverse the damage. It was a lucky thing, and 25 years on I have better security and backup processes.
I still regret that. #family, right?