Here are some examples of words with the prefix "mal":
* malady: a disease or illness.
* malcontent: a person who is dissatisfied and rebellious.
* malformed: abnormal in shape or form.
* malicious: having or showing a desire to do evil to others.
* malpractice: improper or negligent treatment by a professional.
* malnutrition: a condition that results from an insufficient or unbalanced diet.
* maltreat: to treat badly or cruelly.
* malfunction: a failure to function properly.
As you can see, the prefix "mal" consistently adds a negative connotation to the words it precedes.