According to this, the antonym would be Malus. But is there a more widely used term?
Consider an exam where you've got a "Bonus question", so solving it correctly gives you an extra point. Would it be called a "Malus question": solving it incorrectly deducts a point (as opposed to giving no points)? Or is there a better way to describe that?
Best Answer
"Penalty"
http://www.thesaurus.com/browse/bonus?s=t
Interesting concept, "Penalty Avoidance Question".