Painful, a.
1. Full of pain; causing uneasiness or distress, either physical or mental; afflictive; disquieting; distressing Addison.
2. Requiring labor or toil; difficult; executed with laborious effort; as a painful service; a painful march.
3. Painstaking; careful; industrious. [Obs.] Fuller. A very painful person, and a great clerk. Jer. Taylor. Nor must the painful husbandman be tired. Dryden.
Syn. -- Disquieting; troublesome; afflictive; distressing; grievous; laborious; toilsome; difficult; arduous. -- Pain"ful*ly, adv. -- Pain"ful*ness, n.
Shades of meaning
Fernald lists painful only as an antonym, under delightful.
He lists it without comment; the entries above explain its neighbors.
Synonyms
none given