Imbitter :: Imbitter (v. t.) To make bitter; hence, to make distressing or more distressing; to make sad, morose, sour, or malignant..
Imbitterer :: Imbitterer (n.) One who, or that which, imbitters..
Imbitterment :: Imbitterment (n.) The act of imbittering; bitter feeling; embitterment.