Superman has taken down some of the biggest threats in the entire DC universe. Darkseid, Imperiex, Mongul and Orion have all caught the hands of DC's boy in blue, and all profoundly regretted doing so. Even when Supes isn't the figure beating a powerful villain, he's usually there to lend his aid - even if that's just some words of country-farm wisdom before he's on his way to the next impending threat.
But this doesn't mean the Man of Steel is indestructible - that's why he's called the Man of Steel, and not the Man of Diamond, or even graphene. Much like steel, Superman can be broken by just about anybody, even those who don't have insane superpowers equatable to Supes himself.
Between villains like the Joker, heroes like Batman, and surprising additions like Lois Lane's dad, there's a surprising roster of figures who have defeated Clark Kent during his superhero career. And as surreal as it feels to watch him be beaten, it's also not necessarily a bad experience, because it reminds us that with the right mindset, you really can do anything - even deck an imaginary spaceman square in his perfect jaw.