When used individually neither the Single-answer nor the Multiple-answer Multichoice question can result in a negative score no matter how much you add negative grade to the options and how bad the student answers.
If the question is a random question and takes it questions from a question bank category with multichoice questions values below 0 are generated. This does only apply to the Single-answer Multichoice questions.
To replicate: Import the attached course and enrol a user with role editingteacher and a user with role student.
As student, go to the quiz and choose just the bad answers. Submit the attempt.
As teacher, go and see the quiz attempts.
WHAT YOU EXPECT: the student gets mark 0 for the question.
WHAT ACTUALLY HAPPENS: the student gets a negative mark for the question.