What is the most impactful mistake you ever did in your code?

Mistaking Double with double ohhhh boy painful.

https://devrant.com/rants/639677/...

here you go :D

Recently?
CEO rushed me to push something to production (that wasn't even needed, but he was in panic mode) and I neglected to close a block while writing his quick fix.

6.5k errors within the ~35 sec it took to push a fix.

I haven't forgiven him.

When I started working, I used a clob where a varchar would’ve sufficed without understanding how it works or where it should be applied. Brought the application for a couple of hours.