My first ever Rick 4001, a second-hand one. Hated it simply because it sounded so weak. Lasted about four months and flogged it for what I paid for it to Rush fan.
Washburn B-20 8-string. Buzzed like a hornet's nest and broke three octave G strings in a row. Went back to the shop.
Alembic Series I Point. Truly, I hated it. Traded it for a Status Series II.
Though I didn't quite hate it, a Chapman Stick 10-string, bought with the above on a deal. Figured it would be easy to play, having been a piano player but I could barely get a note out of it. Gave myself 6 months to master it and failed. Traded for a Yamaha DX7 !!
Though not a bass, a Rick 360. Bought on a whim and sold real quick.
Another guitar. An SRV Partscaster bought from OZ. Seller withheld a serious mis-match between neck and neck pocket which I had to personally rectify. The only good thing about it was the set of Slider Strat pups on an aged 'plate. Got it playable but the damage was done and I parted it out, losing money.
But the only bass I bought that was POS on arrival was an Alden Beatbacker. Again, bought over the 'net on a whim. Poorly made, poorly finished and impossible to play. That got sent back same day!