Bludgeoning Angel Dokuro-chan (2005)

Original title: 撲殺天使ドクロちゃん

In the future, a man named Sakura is destined to create the technology for eternal life, which (due to Sakura's lolicon tendencies) freezes all women's aging once they turn twelve. God refuses to allow this, so he sends his angels to the past to kill Sakura before he can do this. But one angel, Dokuro-chan, decides to try to change the future without killing him. Problem is, Dokuro is very temperamental, and is constantly killing Sakura (and lots of other people too) in incredibly bloody ways with her giant spiked club. Good thing she can bring people back to life - if only to gruesomely kill them again the next time she loses her temper.