I studied computer science. I had two group projects where I had to do the work of 5 people myself.

The first one was a massive group project, representing 80% of the unit assessment. We were randomly assigned our groups (this always turns out well). Up to this point, I'd gotten high distinctions (80% or better) in every unit and I approached the lecturer to ask what I can to to protect my average if my teammates weren't as committed as I was to getting a good grade. He told me to accept that I won't get an HD because almost nobody does in this unit. Advised that obsessing and taking over everyone's work would likely damage my mental and physical health.

Two were decent programmers but didn't contribute a single line of code (or anything else) to the project because they always found more interesting things to be doing. I wasn't sure how the other two had made it this far through the degree because I had to re-write everything they did (both code and documentation). I wasn't just being a pedantic bastard. Their code didn't work and their writing was incomprehensible.

The lecturer was right about the health effects. I barely slept that semester. On the bright side, I got an HD (and so did the other useless bastards).

The second I also got a terrible group but it was my own fault. The classes for this unit conflicted with another. I just caught up online. However, I'd missed the class where groups were chosen for this assignment and by the time I tried to get a group I only had the dregs left. I met one of my 4 teammates once when I started the project and then they all were good enough to show up for the presentation. Other than that I worked completely alone, again earning my teammates HDs.

The following semester we had an assignment which could optionally be done in pairs. One of the barely-existent teammates from that group project approached me and asked, since we made such a good team last time, whether I'd like to pair with him. I politely declined.