10 Justice League Villains MORE Powerful Than Darkseid

That's right.

While not technically a villain, Batman has the planning and strategic acumen to overcome the Justice League, as most famously displayed in Mark Waid's Tower of Babel storyline. Here we learn that Batman has contingency plans for each individual member of the League, should they turn evil. A pretty understandable precaution given the number of times super-powered characters such as Superman have turned against their allies due to mind control or some such contrivance.

The many failsafes he has for the League members include magnesium conversion nanites for Martian Manhunter, which catch light on exposure to air (fire being his main weakness), a version of Scarecrow's fear toxin which renders Aquaman hydrophobic, and a special version of Kryptonite which turns Superman's skin transparent, overloading him with solar radiation and sensory input.

Due to the overwhelming advantage of his tactical prowess and capability to foresee and prepare for any offensive strategy, of all the characters in the DC Universe that have a legitimate chance of taking down the Justice League, Batman's number one.