forefront vs front end

forefront and front end both are nouns.

Word	Noun	Adjective	Verb	Adverb
forefront	Yes	No	No	No
front end	Yes	No	No	No

As nouns, front end is a hypernym of forefront; that is, front end is a word with a broader meaning than forefront:

Other hypernyms of forefront include forepart, front.

forefront (noun)	front end (noun)
the position of greatest importance or advancement; the leading position in any movement or field	the side that is forward or prominent
the part in the front or nearest the viewer