A "powerful witch" refers to a person, usually a woman, who possesses a great amount of magical abilities and knowledge. They are skilled in casting spells and using their powers to influence events or individuals. Full definition
Alex is a bruja, the most powerful witch in a generation — and she hates magic. (booklistonline.com)
I couldn't have a bunch of powerful witches — excuse me — brujas, running around Brooklyn uncontrolled. (bookpage.com)
Cassie (Britt Robertson) moves to Chance Harbor, Washington, after her mother dies and discovers she is one of several high school girls who descend from powerful witches, in the drama based on the books by L.J. Smith (who also penned the Vampire Diaries books). (metacritic.com)