Gnomish
taura
adjective. powerful
baldrin Archaic
adjective. mighty
polodrin
adjective. mighty
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 word appearing as G. polodrin “mighty” in the Gnomish Lexicon of the 1910s, an adjective form of G. polod “power, might, authority” (GL/64). It had an archaic variant {poldurin >>} †polurin or polorin which was sometimes used as a sobriquet for Tulcus.
Neo-Sindarin: Since ᴹ√POL(OD) still had to do with “strength” in Tolkien’s later writings, I’d adapt this word as ᴺS. polodhren “mighty, ✱powerful” for purposes of Neo-Sindarin using the later Sindarin adjective -ren. Given the meanings of its base noun (including authority), I’d assume this adjective has a connotation of political power. I’d constrast it with S. belaith which I’d use for “mighty” in general (independent of authority).