And yes for justice for all families and people who loved the characters that killed by Nana, Nana is deserved to has redemption but punishment is inevitable. I bet she will beated up or tortured by Nanao until Nanao deciding he will forgive Nana and Nana will go to jail or executed in the end of manga for her crimes. But I don't want Nana to die, punishment is okay but please don't die, she is just a victim that framed by Tsuruoka to kill under his order.
She was brainwashed and under pressure to not be able to fight back against Tsuruoka. We must know how does it feels to be brainwashed, not knowing the truth and then regret. She was being fooled to think killing them was OK by Tsuruoka. She even said that she don't want to killing anymore infront of Tsuruoka right? it means, she already don't want to kill anymore but Tsuruoka still insist her to do that.
I love this. Yeah she regrets, sure she sees that she's done wrong things. I'm not denying that, I just hated her the moment she killed nullifying dude, she continued to kill innocent people, people who have done nothing wrong. People who had families that probably loved them, regretting it does not turn back time, regretting it does not bring them back. The only reason she cared is because someone she started to like died. You see that's karma, karma is like the Grim Reaper. She understood the feeling of losing someone, of losing someone important. Those innocent/maybe not innocent people probably had people who loved them.