Mal- means bad or badly, wrong, ill

malady (n) - a sickness or illness; bad health

malefactor (n) - a person who does the wrong thing; an evil person

malevolent (adj) - wishing evil or bad will for others; mean

malfeasance (n) - bad conduct or wrongdoing by a public official

malfunction (v) - to function imperfectly or badly; fail to operate normally

malice (n) - a desire to do something bad to someone else; doing something that is wrong on purpose

malignant (adj) - very bad or harmful; likely to cause death

malnutrition (n) - a poor diet; bad eating habits that result in poor health

malodorous (adj) - stinky; having a bad smell

malpractice (n) - an instance of bad conduct or treatment from a doctor or other professional