As I said, Esdeath doesn't count. She's an antagonist, she can be as OP as the author wants her to be. And that's great. It makes for good entertainment.
Leone can recover from almost any wound, but when she faces an opponent she can still get a rough beating. And she has taken a few of those.
I agree with you that Akame is too OP, and believe me that does bug me, indeed, it's one of the things that bug me about this series.
As for Pumpkin, yeah, in concept its not that OP. In action, it was pretty much f*cking OP. There was practically no way to kill Mine if she so much as noticed anyone sneeking up on her. The fact that the only way she could have been "taken out" was by having her gun draining her life force tells you everything you need to know