A noun for “slaughter” in the Early Noldorin Word-lists of the 1920s, an elaboration of ᴱN. rhanc “corpse” (PE13/152).
Early Noldorin
dagros
noun. slaughter
rhangos
noun. slaughter
There are more words but they are from Tolkien's earlier conceptional periods. Tolkien likely changed these words as he evolved the aesthetics and completeness of the languages. You may even find languages that Tolkien later rejected. Do not mix words from different time periods unless you are familiar with the phonetic developments.
Below: Tolkien's Late Period (1950–1973). These are from Tolkien's late conceptual period — his most settled forms of the languages. Prefer these over the earlier ones above when composing new text.
A noun appearing as ᴱN. dagros “slaughter” in Early Noldorin Word-lists of the 1920s based on the verb ᴱN. (n)dag- “to slay” (PE13/141). It also appeared in the contemporaneous Early Qenya Phonology (PE14/66).
Neo-Sindarin: For purposes of Neo-Sindarin, I would update this form to ᴺS. dagras using the later abstract noun suffix -as.