Rirenil, you just tricked me into watching a video about character development in My Little Pony. Also, that guy clearly does not read comics. Superman is the worst character in comic history. But it's not that he's a Mary Sue. The writers can never settle on who the man actually is. And eventually, one becomes sick of seeing characters reincarnated. He needs to die.
Permanently.
DC is seriously just bad with the writing side of comics. Superboy Prime punching heads off and bisecting people with his eyes... F*** that.
And then they try to redeem characters like this.
So I came back to say that the worst Mary Sue (in DC comics) is Batman. Think of all the symptoms of Mary Sue-ism. Dead parents, born rich and famous, ridiculous morals, highly intelligent, considered just as powerful as Superman despite being human. He barely seems human. If the man didn't have his villains, he would have no personality. I've heard it said that the villains are what make his character. Without them, he'd be nothing.