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Cartographer
Successfully is a 12 letter word with three set of double letters. Stubbornness is another 12 letter word.
Cartographer (?)
exasperating, antagonizing
Ranidaphobia is fear of frogs (12 letters).Batrachophobia is another word (14 letters).Frog phobia is also used (10 letters, but two words).
The letters spell listlessness. The word uses all 12 letters.
manufactured
The word biochemistry contains 12 letters.
Crucifiction=12 letters
manufactured
manufactured
The only English word I could find that meets the criteria is candleholder, but I am not sure it is a hospital helper.