I don't expect you to tell me the ending in detail. Since those are mysteries I suppose a bad end is one where the culprit isn't caught or an ending which causes even more pain to the reader and characters at the revelation of who the culprit is. I don't want mysteries that can be too scary with too many bloody deaths.

[You know like... A story which has people's faces being smashed and teared down, the culprits are the parents of the child that was raised by the only survivor and a banquet was made out of body parts.]