puissant

puissant \PWISS-uhnt; PYOO-uh-suhnt; pyoo-ISS-uhnt\, adjective:

Powerful; strong; mighty; as, a puissant prince or empire.

As an upcoming young corporate lawyer in San Francisco in the 1930's, Crum tended the interests of some of California's most puissant businesses, starting with William Randolph Hearst's newspaper empire.
-- Richard Lingeman, "The Last Party", New York Times, April 27, 1997

If we are to believe that country's literary pundits, "irreparable damage to a great British institution" may soon be done by an invading army more puissant than Hannibal's or Alexander's, an army Marching out of the creative writing schools of American universities, leaving Will Shakespeare's sceptred isle "smothered amid a landslide of books from the US".
-- Jonathan Yardley, "Bring on the Yanks", The Guardian, June 5, 2002

Puissant is from Old French puissant, "powerful," ultimately from (assumed) Vulgar Latin potere, alteration of Latin posse, "to be able." The noun form is puissance.