The text you provided does not explicitly mention a specific 'lord of the rings creature' by name that fits with all or most of your key terms.

However, based on some general information about bears in The Lord of Ring's universe as well as parts from your description I'll try to make an educated guess:

Bears are indeed large and ferocious creatures featured prominently throughout Middle-earth. They appear frequently in the works of J.R.R Tolkien such as The Hobbit and The Fellowship of the Rings.

Given that you mentioned 'lord' which could be interpreted as lordship or control over these bears, Beorn who can shape-shift into a bear-like creature might fit this description fairly well. However, it's worth noting that in many cases when talking about powerful beings with direct control over animals they are often referred to as 'lords of X', where X is the specific animal(s) under their dominion.

Another possibility could be Sauron or other dark lord characters who sometimes had some degree of influence over bears and other ferocious creatures. However, without more information from your provided text it's difficult to make a definitive conclusion about which character specifically you are referring to.

Lord of the rings creature 3 letters