The second part of this episode begins with Batman showing why he's the brains of the team, but fortunately Amazo isn't kept down for long. If anything, the second battle against Amazo is even more impressive, as the League seems to have their act together this time around and fights the android to a standstill before Luthor arrives - making up for their poor showing (before Superman shows up to bail them out) the first time around.
As becomes clear in this episode, and is clear in retrospective for the first episode, is that Amazo is "evolving" and growing. There are some subtle hints of this in part 1, when it takes on the face of its father figure, Lex. This time we get it "adapting" Flash's ladykiller persona (somehow, despite a visual scan, but go with it), then its starting to question Lex, and then adapting/evolving to overcome the kryptonite. This sets the stage for Amazo to duplicate the powers of the cosmos and fly away at the end, its "evolution" complete.
Lex Luthor doesn't play a really large part in this episode - much of his role could have been played by any villainous characters. Here he plays Lucifer, corrupting Amazo. Still, it's nice to see Lex's storyarc moving along, which will lead to the events of "A Better World."
The other theme of the episode is "humanity" - Amazo gains humanity of a sort and then rejects it to become something greater, while J'onn is forced to cope with being exposed to the full spectrum of humanity's thoughts and impulses. Presumably he is just overwhelmed by the sheer volume of it, since he's scanned the minds of major villains before. While J'onn doesn't become "human" himself, he accepts humanity for what it is, and the final hug with Wonder Woman seals the deal. Hopefully they'll do something with this in future.
Overall, "Tabula Rasa" is another in a fairly stream of good episodes that we've had since late in Season 1, and look to continue.