The negative value is the worst. I was working on a project with someone. I'd check in periodically. After a couple weeks, he fesses up and tells me he hasn't been able to get very far, but things are "mostly done", I "just" need to test it for him and integrate it with the rest of the system. By mostly done, he meant the code had no tests and was never even run manually. In fact, the code would not even execute due to syntax errors.

I had to spend another week and a half reworking things. I got it to work well enough, but it would've gone smoother if he hadn't been involved at all. The result was crap.