I don't know how to feel about this ending. On one hand, I liked seeing the demise of the pink-haired chick and the ex-fiance. Unlike some of the comments here, I didn't mind not seeing them die/get killed. Seeing them slowly ruin each other's lives was much more satisfying than a swift death.
On the other hand, I don't like how things ended with the vampire hunter. I thought that she'd stay with him until he died (like when she stayed with Gu Chen). I suppose her objective this time was different (find true love vs. keeping the vampire clan alive) so she felt no need to stay as long. At the very least, I thought she'd convince him to stay as a human. I don't really get why she'd let him become a vampire. It would either go two ways: 1) she never wakes up and he waits for her forever not knowing she won't wake, or 2) the original owner of the body returns. Either way, it's really sad for the vampire hunter because she won't be with the woman he fell in love with. I think it was cruel of her to let him abandon his humanity when he isn't even going to end up with her.
I guess she just doesn't care about him at all? I got the impression from the previous two arcs that she somewhat cared about the relationships she developed (i.e. her adopted son in the first, and Gu Chen in the second) so that was the reason why she didn't immediately leave the world. Like, she stayed for about 10 years in the first, and to the death of Gu Chen in the second. She had no reason to stay behind when she completes her missions, which is why I thought she stayed because she somewhat cared about them. But in this arc, she stays for less than three years and even misleads the guy into thinking they'll meet again. I'm just confused about her character and the inconsistency. Although I don't expect much character depth in this series, I hope future arcs would help me understand her better.