Characters never followed up on
There were some very dangerous characters but because the story had some time travel, the horrible timelines and fates were erased.
Two that come to mind are Nathaniel Pratt and Baccara.
The sisters could have kept their eye on Pratt even after changing the dog walking, but never did. With Baccara, they don’t even know about him at all. He is just a bum demon wandering around but maybe the writers could have went back to him and his potential.
Any other characters or even small storylines that could have been more?