It's really easy to contribute negatively to a project. On the business end, I've worked with people who changed priority/direction/feature-sets so frequently that they actually made things worse; the project would have been better without them, hence a negative contribution.
On the technical side, have you never worked with a programmer that insisted on introducing his favorite framework/language, or declared that the "current code sucks, it needs to be re-written"? That's potentially a negative contribution. Hell I've even been that guy. It's not only possible, it's common.
In my experience, rewriting code almost always ends up a net positive.
I think the negative influence is usually more in line of those who resist change such that so much cruft accumulates, that it truly becomes too dangerous to change anything.
Sure, but if the person actually had the idea that created the entire venture, it can't really be negative unless their influence runs it to the ground and puts the company in debt, I guess.
On the technical side, have you never worked with a programmer that insisted on introducing his favorite framework/language, or declared that the "current code sucks, it needs to be re-written"? That's potentially a negative contribution. Hell I've even been that guy. It's not only possible, it's common.