I'm not sure exactly, but there are a few. You might want to check with the official publisher or dedicated comic book databases for an accurate count.
One of the most terrifying tales might be the one about the haunted house. The way the author describes the creaking floors and the cold drafts that seem to have a life of their own is really spooky.
The Sabrina comics have elements of darkness. For instance, the portrayal of evil forces and the conflicts Sabrina has to overcome can create a darker atmosphere. However, it also balances this with moments of friendship and personal growth.