1) Backbiter 2) Candidate for a suit 3) Defamer 4) Depreciator 5) Detractor 6) Disparager 7) Knocker 8) Maligner 9) Maligner of a sort 10) One vilifying in print 11) Slanderer 12) Traducer 13) Vilifier 1) Backbiter 2) Defamer 3) Maligner 4) Slanderer 5) Traducer 6) Vilifier 
• (n.) One who libels.
Li'bel·er (-ẽr) noun One who libels. [ Written also libeller .] ' Libelers of others.' Buckminster. 
libeler 1. Someone who libels another person. 2. A person who publishes a libel assailing someone else.