The worst rejection was one after a first interview and a subsequent 3 hour code challenge. I was super nervous as it was my first code challenge in an interview that was one of my first. I wasn't confident when I submitted my work, but the time was up and so there wasn't much to be done.

The rejection was simple. Pure silence. No arguments, or feedback. Just didn't hear nothing back and that didn't help my fresh out of university self-confidence.