You are forbidden to relate anything derogatory about others.  If a derogatory statement is true, it is termed loshon hora.  If it is false, even partially so, it is termed motzi shaim ra (defamation of character) and the offense is much more severe.

It cannot be repeated often enough that true derogatory statements are considered lashon hora.  The most common defense to a rebuke for speaking lashon hora is, “But it is true.” That is exactly what categorizes the statement as being lashon hora! ~ Guard Your Tongue by R’ Zelig Pliskin