Harry Potter: 15 Most Powerful Wizards In The Wizarding World
6. Alastor Moody
Though we arguably see the best of Alastor Moody when he's actually Barty Crouch Jr in disguise, Mad-Eye was the most famous Auror of modern times (presumably until Harry Potter became one). And you don't get that sort of reputation without some serious credentials to back it up - even if it does cost you a couple of body parts.
Moody was a one-man army against the Dark Arts having personally sent many of Azkaban's most notorious criminals there, which is precisely why Lord Voldemort believed he would be guarding the real Harry during the Battle Of The Seven Potters. So in essence, it was his power that got him killed.
And Voldemort had good reason to believe it: Mad-Eye was an expert in Charms, Transfiguration, Defensive Magic, Herbology, and Potions. Even in death his protective charms on Grimmauld Place were so strong even Voldemort couldn't penetrate them.