even so vs nevertheless

even so and nevertheless both are adverbs.

Word	Noun	Adjective	Verb	Adverb
even so	No	No	No	Yes
nevertheless	No	No	No	Yes

As adverbs, even so and nevertheless are synonyms defined as:

even so and nevertheless: despite anything to the contrary (usually preceding a concession)

Other synonyms of even so include all the same, at the same time, however, nonetheless, notwithstanding, still, withal, yet.

even so (adverb)	nevertheless (adverb)
despite anything to the contrary (usually preceding a concession)	despite anything to the contrary (usually preceding a concession)