Top Health Malefits of ____
OED with prefix mal+ ‘ill’, ‘wrong’, ‘improper(ly)’:
Self-conscious use as an antithesis to benefit n.
detriment, disadvantage, encumbrance, hindrance, nuisance, obstacle
Antonyms: advantage, aid, assistance, benefit, boon, foredeal, help
Something that is harmful or disadvantageous.
Merriam-Webster has no entry for it, but upon search suggests malefic ‘malignant’, ‘malicious’. The related actor term malefactor, it lists of course.
So the word fits in well with other mal+ terms, although some readers may mistake it to relate to male instead.
Other associations people may have are Maleficent, the evil fairy in Disney’s 1959 adaptation of Sleeping Beauty and later installments of the franchise, and the board game Malefiz that is also known as Barricade.