Beware, older languages below! The languages below were invented during Tolkien's earlier period and should be used with caution. Remember to never, ever mix words from different languages!

Gnomish

fectha-

verb. to destroy, ruin, spoil

A verb appearing as G. fectha- “destroy, ruin, spoil” in the Gnomish Lexicon of the 1910s, related to G. fêg “bad, poor, wretched” (GL/34) and thus probably based on an unattested the early root ✱ᴱ√FEKE.

Neo-Sindarin: For purposes of Neo-Sindarin I would adapt this verb as ᴺS. feitha- “destroy, ruin, spoil” based on a Neo-Root ᴺ√PHEK, with the vocalization of ekth to eith.