It's a little unsure what it wants to be.
Scarlet is about a highly trained badass assassin who preys on corrupt cops. No wait, it's about a victimized young woman with a message of revolution and anti-corruption. Fight the system!

[SPOILERS ahead] In the first panel, she skillfully and remorselessly kills a man. And beats the shit out of a bike thief for good measure. Scarlet then speaks directly to the reader while recounting her story, why she is what she is and does what she does. And it turns out that she has no training. She's just a kid whose boyfriend was murdered by a corrupt cop looking for a convenient patsy. She's pissed and starts attacking corrupt authority figures with an absurd level of success.

It's kind of a strange message. It shoots for "Give up your apathy!" but lands on "What's could go wrong with serial vigilante murders? Give it a try!"

Bendis uses some nifty framing: 12-panel spreads that sum up someone's life, Scarlet describing events out of order and as they happen to her... It has an interesting look, lots of muted grays and browns except for her bright orange hair, which pops. I think Scarlet uses that photo-conversion process from Ex Machina, or something similar.