The entire stretch from Barkakhana upto Nagar Untari and up and until Renukut, is stunning. I have never got the opportunity to travel on the Ranchi-Tori line so I cannot comment on the beauty of the rail route there.
Another route that has the potential to be a very beautiful route is the proposed Dhanbad-New Giridih line via Tundi. However that project has seemingly gone into limbo!