There are people that use their powers for good and there are those who use it for bad, and the battle between good and evil is like a never ending game of chess.
Even before Supers were legalized, the world has dealt with crazy shit for the past few weeks, The Titans and Raven finally defeating Trigon and the Brotherhood of Evil, Danny Phantom and millions of ghosts turning the world intangible to save it from an asteroid, Spider-Man defeating the Green Goblin, but at the cost of Harry Osborn losing a father, Kim Possible and her friends fighting off the Warhawk, Jake Long developing his dragon powers, a mysterious teenage vigilante named, "The Keyblade Holder" protecting the streets of Chicago, Ben Tennyson gaining the Ultimatrix and defeating Vilgax for good, and lastly, the Parrs fighting off Syndrome.
And even before supers were legalized, villians have been terrorizing the world, from Vlad Plasmius blackmailing the world, Syndrome killing heroes, Spidey's rogues' gallery terrorizing the city of New York, Slade and several others terrorizing Jump City, and etcetera.
Even so, the heroes were able to stop them. Superman outsmarted Luthor, Batman lured Joker to a trap, Avengers stopped Thanos, ETC. But it's just the beginning of a long, continuous battle between good and evil.
But ever since Mr. Incredible and Elastigirl legalized Superheroes, the same question has been repeating in everyone's heads...
"Is it really surprising that the world's most powerful beings should be figures of controversy?"
There were still people afraid of heroes going rogue and beginning a regime of their own. There are still people who think that Heroes are just nothing more but a game for superpowered beings to play in order to take over the whole world.
But when the Justice League, Avengers or even the CIA aren't enough to stop the most dangerous foes, the world's adolescent super powered beings will have to join forces to stop Slade and the Green Goblin and their team of super criminals.