in the end vs ultimately

in the end and ultimately both are adverbs.

Word	Noun	Adjective	Verb	Adverb
in the end	No	No	No	Yes
ultimately	No	No	No	Yes

As adverbs, in the end and ultimately are synonyms defined as:

Other synonyms of in the end include at last, at long last, finally.

in the end (adverb)	ultimately (adverb)
as the end result of a succession or process	as the end result of a succession or process
eventually or after a lengthy period of time