【Frown】 ,  【scowl】 ,  【glower】 ,  【lower】 ,  【gloom】  are comparable when they mean to put on a dark or malignant countenance or aspect.

【Frown】 commonly implies a stern face and contracted brows that express displeasure, disapprobation, anger, or contempt.

【Scowl】 carries an implication of wrinkled drawn-down brows that express ill humor, sullenness, or discontent.

【Glower】  implies a more direct stare or gaze than  【frown】  or  【scowl】 and carries a stronger connotation of anger, contempt, or defiance.

【Lower】 implies a menacing darkness and sullenness of face or of aspect; the term is used in reference not only to persons but to skies that give promise of a storm.

【Gloom】  ordinarily carries a much stronger implication of gloominess or dejection and a much weaker (often nonexistent) suggestion of threatening than does  【lower】 .