Lena realizing the depth of her descent into becoming like Lex echoes Harvey Dent's famous quip in The Dark Knight (2008) that one either dies a hero or lives long enough to see themselves become the villain.
Lex asking Brainy if it's "Leviathan goes to Washington," is a reference to the film "Mr. Smith Goes To Washington" from 1939 starring Jimmy Stewart about a naive man becoming a senator and going to Washington D.C.