Mr. Ring called attorney general, Mr. Cary, a slanderer and coward, knowing he was absent.
From the thenewstribune.com
Hurting someone's reputation by lying makes the slanderer a genius?
From the en.wikipedia.org
A person who harms another's reputation may be referred to as a famacide, defamer, or slanderer.
From the en.wikipedia.org
The slanderer must remain married to his wife Deut.
From the en.wikipedia.org
But now I am writing you that you must not associate with anyone who calls himself a brother but is sexually immoral or greedy, an idolater or a slanderer, a drunkard or a swindler.
From the blog.beliefnet.com
More examples
Defamer: one who attacks the reputation of another by slander or libel
Defamationu2014also calumny, vilification, and traducementu2014is the communication of a false statement that harms the reputation of an individual person, business, product, group, government, religion, or nation.