Twenty years after the horrific slaying of a family, terrified townsfolk wait in fear for the imminent return of the menacing monster that was put away for the crime.

A suggestion not only of logline structure and detail but possible story elements:

"An inexperienced small-town deputy must protect his community from an escaped murderer seeking revenge on those who captured him."

It will serve your story to make the protagonist an underdog. Stack the deck against him. Think of a reason the Sheriff can't handle it, like maybe he retired, or died, or moved, and no one's replaced him yet, or the main character is the inexperienced new Sheriff?lots of ways to set this up.

Why not a female Sheriff? A young woman in law enforcement no one thinks can handle herself, and she manages to defeat the big bad monster guy against all odds? That's a compelling story. Maybe your script has these elements already, but the purpose of the logline is to present these elements as quickly, simply, and clearly as possible.

"...News about the release of the monster..." is a weak inciting incident as it is not a distinctly visual event that can occur to the MC perhaps he discovers the mutilated body of a person he cares about this wold be powerful enough to motivate the MC to take action.

"...The slow and painful wait..." So High Noon basically. Not sure this wold work well now days though.

I think the difficulty in the structure of a logline for this concept lies in a lack of appropriate motivation and descriptions for the MC.

When I read "...clan leader..." I thought this is set amongst native Americans in ancient times or cave people but it actually is a modern day story. Why clan? Can he not just be the local law officer that actually swore to protect the town? Who may have actually put the bad guy in jail in the first place? Perhaps a local lawyer who had him put in jail for many years? Etc...

Secondly as Nick mentioned there appear to be no personal stakes for the MC. Look at Cape Fear similar premise the MC must protect his daughter and wife it is not just a professional motivation for him.

Describing the MC as "...brave..." is again a generic description because all MC must at some point to some degree "be brave" to take on the challenge of achieving their goal. What is his character flaw? What will be his inner journey?

Thanks Clint Cure, you're right and that is a similar premise to this story i.e. people of a small town fearfully wait for the the killer who is to returning to punish the people who put him away. They turn to a powerful figure in their community to stop their old nemesis.

I'm finding it difficult the get the right logline.

If you wanted to explore it a bit more here's a couple of similar premises but with different main protaganists, Redhill - the MC is a rookie policeman waiting for the escapee to show up (or something like that) and And God Said to Cain - the MC is the character returning to the town. You can have a movie about a town 'waiting'. In fact God Said to Cain is just that and is intense as hell. It is a Western directed like a horror movie.

Another rewrite:

'A brave clan leader of a quaint town must face off with his nemesis, a brooding convicted killer out to settle an old score, in a fight til death.'