DM had an elderly godmother, M, who was a wealthy widow, no children, and she eventually went into a care home. DM used to see her regularly, but didn't need to do much for her, because she had G, a retired accountant and friend, who was an "absolute treasure", looked after her accounts and whatnot. G managed to become M's PoA and he was the sole beneficiary of her will. DM was fine with that, as long as M was happy and safe.
Over the course of a year or so, it became clear that G was not running M's finances for M's benefit, but in fact, he was feathering his own nest. It came to a head when DM went to see M and found her in tears - she didn't even have enough money to pay for her weekly hair appointment or buy a newspaper. She confessed to DM that she though maybe G wasn't running things as he should. So DM looked into it.
Well, it turned out he was billing her a huge amount for his "services", and had been steadily milking M's bank accounts to the tune of over £50k. Ridiculous, inflated charges. M was devastated, and changed her will, so when she died a year or so later, G got nothing. The irony is, if he'd just kept M happy during her lifetime no-one would have ever found out, and he would have got all her money eventually. But he was just too greedy to wait.
G got his comeuppance, and was prosecuted and convicted of fraud... he couldn't pay all the money back, but a lot was recovered.