The opposite of ill is well.
more opposite, most opposite handsomer, handsomest more ill, most ill farther, farthest or further, furthest more excellent, most excellent
The opposite could be unhealthy, sick, ill, or afflicted.
healthy
The opposite of prepared is unprepared, meaning unready or ill-equipped. (In cooking the opposite of prepared is raw or uncooked.)
ILL ?
the answer to that is very simple it is ill
The opposite of sane is insane, which refers to someone who is mentally ill or not of sound mind.
ill say a positive number
The opposite of goodwill is ill will, which refers to having negative feelings or intentions towards someone. It is the opposite of kindness, generosity, and positivity.
ill
Opposites could include: unwell ill sick poorly ailing indisposed
The opposite of naughty would be well-behaved, or good. For Santa Claus, the opposite of naughty is "nice."