Frightfuly or Frightfully: How To spell?
The word Frightfuly is misspelled against Frightfully, an adverb meaning "In a frightful manner; to a frightful dagree."
Frightfully has double "ll" is mispronounced as "l"Remember double 'LL' in between the strings frightfu & y which should not be misspelled with single 'L'
Wrong Spelling:  frightfu-l-y  Correct Spelling:  frightfu-ll-y 
Check more misspelled words of Frightfully to spell it correct.