Opposite of "Attractive/Pretty"
Unttractive/Ugly
Opposite of "Reliable"
Unreliable
Opposite of "Fast"
Slow
Opposite of "Quiet"
Noisy
Opposite of "Simple/Easy-to-use"
Complicated
Opposite of "Flexible"
Inflexible
Opposite of "Light"
Heavy
Opposite of "Modern/Up-to-date"
Old-fashioned/Out-of-date