Kevin Costner and Christine Baumgartner recently finalized their divorce after 18 years of marriage.
Baumgartner allegedly feels shortchanged by the divorce settlement.
She is reportedly on a "revenge mission" against Costner.
Baumgartner is allegedly badmouthing Costner's skills in bed.
She wants to make him the "laughing stock of Hollywood" with her comments.
Sources say she is telling people Costner was boring in bed and selfish as a lover.
Baumgartner feels Costner's fame enabled him to portray himself as a sex symbol
Costner previously directed and starred in epic Westerns Dances with Wolves and Open Range.