The spelling of the word "scummier" follows a common pattern in English where the suffix "-er" is added to a base word to indicate the person or thing that performs the action. The base word here is "scum", and the "-ier" ending changes to "-i-" when the suffix "-er" is added. The correct pronunciation of "scummier" is /ˈskʌmiər/, with stress on the first syllable and a schwa sound in the second syllable. This word is commonly used to describe a person who engages in dishonest or unethical activities.