Modifiers matching grump:

• fastidious,
• grouchy,
• wealthy,
• rich,
• covetous,
• penny-pinching,
• greedy,
• arrogant,
• mean,
• ill-tempered,
• misanthropic,
• miserly,
• gruff,
• jealous,
• impatient,
• heartless,
• principled,
• condescending,
• grizzled,

Simple categories matching ill-tempered:

• person,
• grump,
• tyrant,