Is There a Word Libeler?

a person who libels; a person who publishes a libel assailing another.

What is a Libeler?

Legal Definition of libeler

: a person who makes or publishes a libel.

Is there such a word as ineptitude?

Ineptitude is a lack of skill, ability, or competence. A doctor would prove his ineptitude at practicing medicine if he mistakenly removed a patient's spleen instead of his kidney. Ineptitude and incompetence are synonyms to describe people who have absolutely no idea what they're doing.