unappreciative (adj.)

• disappointed
• disapproving
• discontented
• disenchanted
• disgruntled
• disillusioned
• displeased
• dissatisfied
• dissenting
• indignant
• low
• opposed
• opposing
• poor
• thankless
• uncomplimentary
• unfavorable
• ungrateful
• unhappy
• unmindful
• unthankful