apathetic
The definition for apathetic is "Showing little or no emotion." Used in a sentence: Carmine was concerned about his usually cheerful brother's apathetic attitude.
foil
The definition for foil is "One that enhances or underscores by contrast." Used in a sentence: The sweet cookie was a perfect foil to the sour lemon sorbet.
garish
The definition for garish is "Offensively bright." Used in a sentence: The garish wallpaper offended Jerome, who preferred subtle colors.
impenitent
The definition for impenitent is "Lacking remorse." Used in a sentence: The impenitent criminal received a harsh penalty, but his remorseful accomplice was released.
stern
The definition for stern is "Harsh, severe." Used in a sentence: The stern principal canceled the prom after the seniors played a silly prank.