I will not say that Blood-C is a BAD anime. In reality I did enjoy it, but there are several criticisms that left me reeling during and after having watched it.
Firstly, a lot of the violence was rather senseless, to me. It had a very "KILL ALL THE THINGS!" mentality, which is apparent in the first few episodes alone. The fight scenes were enjoyable less for their unpredictability (because they were rather predictable) than for their sheer intensity.
That said, the fights WERE very intense - much more so than they were in Blood+. Dare I say, there is a lot more gore (although much of it is censored out, perhaps thankfully) than in its cousin, Blood+. The main character is a lot more likely to kick ass than Saya Otonashi was.
The revealing of information is a little slow and it isn't very organized. It IS a relatively short series, at 12 episodes, but they could have revealed information at a different pace than they did.
In all, as I said, I did enjoy the anime and I will say that it is good. I feel as though, however, it could be refined and it does not match up to the artwork that was Blood+; at least to me.
