What’s your worst purchase / what bags are you holding? (no meme stocks or pump and dumps)

My personal attitude towards stock market is somewhat like casino (options are back-alley gambling) – you win some, you lose some, but in general you are happy to play the game and be involved (as long as you consider how much you are ready/willing to spend/lose).
I think we’ve all been bag holders of one ore more positions without any hopes of getting out without losses. So far I’ve made just a few unlucky decisions, which were based on my “addiction” to Nordic IPO’s, pure stupidity or lack of research.
So, what are your stories on this? Which were the stocks you were confident in, but eventually the value just kept dropping with no sunlight in sight?
These are mine:
1. $Disney(DIS.US)$ . Really thought it would rebound after COVID19 lockdowns.
That -45% stares me in the face every time I open my otherwise OK portfolio.

2. $Senstar Technologies(SNT.US)$ (lack of research / stupidity) – purchased when I thought “this won’t go any lower” and just kept falling afterwards. Again, I was hoping/looking for a quick gain as I thought “come on, this won’t go any lower”. Had my chance to exit with +15%, but somehow considered that this one should be the one where I could double up.
$Apple(AAPL.US)$ $Dogecoin(DOGE.CC)$ $Coinbase(COIN.US)$ $Tesla(TSLA.US)$ $Twitter (Delisted)(TWTR.US)$ $Invesco QQQ Trust(QQQ.US)$