My worst was leaving some retirement money at Megacorp in their profit sharing. I did that to have a second source of monies when I retired at 56 via rule of 55.
It was a good fund for many years, turns out the fund manager allowed Megacorp to tilt the fund into some hot sidebets. Our existing Megacorp management team had recently retired and the new management team was a bunch of good looking idiots.
They allowed a side bet to become over 50%, yes over half the fund, was allocated to a risky biotech, that went bankrupt! This company borrowed business practices from pharmabro and were shut down.
Thanks to a friend I joined the proper lawsuit and have collected 10k, from the fund managers, to date. I should have arbitration against Megacorp sometime this year. So far we have been winning all the judgements and it looks like people are being made whole. I thought my friend was awarded 100k, I reviewed our communications and the attorneys were awarded 100k for her settlement, she got 250k. Since it'san ERISA protected retirement fund the attorneys fees are awarded separately. I'm glad I got into this suite, about 10k of my former co-workers are in another suite where they will each receive $47. For many this was their entire retirement, they'd been convinced of the safety of this fund.