Worst decision you've made/seen someone make

What's the worst decision making you've done/seen in aviation?

I did vfr traffic patterns once when cloud ceilings were 800 and it was about to rain. Weather was good when I took off, went awry in a matter of minutes. Luckily we were able to get ourselves sorted out safely. Picked up an IFR clearance with instructor's help and it wasn't a big deal. Weather got a bit better and we were able to go back to VFR.

I have also flown in 30 plus knot winds with gusts in a c172 for a landing flight. Don't do this (obvious if you're an experienced pilot, cfi, etc, but at 40h I had no idea what I was doing). I learned the hard way and had to face the consequences of my stupidity.