From what I recall, if my question has at least one upvoted or accepted answer, I am not allowed to delete it even if my question is closed and/or has negative score.
I asked a question recently that was marked as duplicate, and it has a net score of -3 (-4/+1). It has 2 upvoted answers, one of which is accepted (by me). I noticed that it has 1 delete vote, which got me wondering: if I myself the OP am not able to delete this question, and I don't intend to:
Why would 3 high-rep users be able to do so?