even so vs notwithstanding

even so and notwithstanding both are adverbs.

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

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

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

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

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