My worst collab/group project experience definitely has to be my final semester project during my undergrad.

We were a team of 4 including myself and would meet every day to work and every day:

1. My teammates would show up late
2. One of my teammates’ girlfriend lived in my apartment and shed just show up every day and waste our time and make him never contribute (He LITERALLY never did any work and got by with no effort)
3. The other 2 on the team didn’t know anything and never made efforts to learn

I literally did the entire project on my own (Code the full project, make presentations for all the reviews, and teach the other 3 every step of the way).

TLDR: I topped my batch and got 199/200 whereas everyone else were 190 or below, and I went on to publish that project in a Science Journal (Again, with no efforts from the team)