I have so many ME2 saves, I don't know if I'll ever play them all.
I'm planning on trying to get one more where I kill off everyone. I know it can be done.
Including yourself (make sure to get Samara's daughter on your squad). Anyway, don't upgrade your ship. That way, I believe 4-5 people die immediately.
The playthrough I'm doing right now I plan on having everyone live since I didn't do that the first run through. I was trying to make my character be a badass (Infiltrator, all Renegade) but I freaked it up somewhere in the beginning because I was being to nice to people.