Antonyms '-Ful' to '-less'

There are some examples that related with the title...

Careful⏩careless
Cheerful⏩cheerless
Doubtful⏩doubtless
Harmful⏩harmless
Helpful⏩helpless
Hopeful⏩hopeless
Painful⏩painless
Powerfull⏩powerless
Shameful⏩shameless
Thoughtful⏩thoughtless
Useful⏩useless

Its useful right???

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