Hi name may not be as recognisable as some of the other villains listed here, but make no mistake about it, Mongul is a major threat to both Superman and the larger DC Universe. Exiled from the planet he conquered, the villain later set his sights on Earth, and it was that which led to him coming to blows with the Man of Steel. Unfortunately for Superman, Mongul is every bit as powerful as he is, not to mention cunning and ruthless. That became evident when he destroyed Coast City (the home of Hal Jordan/Green Lantern), and he stands out as perhaps the most sadistic villain here as a result. Mongul's desire to bring down Superman at one point led to him attempting to destroy the sun, so of all the alien warlords the hero has faced over the years both alone and as part of the Justice League, this guy stands out as one of the most dangerous by far.
