Board Thread:Questions and Answers/@comment-6312663-20150812131745/@comment-1038387-20150815010236

The Justice League is one team of good guys. There's the Teen Titans, the Justice Society, Shadowpact, the Birds of Prey, to name but a few. And there have been multiple versions of the League, most prominently the Justice League of America and Justice League International. Many characters have lead this team. Superman may be one of the core members of several incarnations, and may be a public figurehead, he usually isn't the leader.

The Legion of Doom is one team of bad guys, popularized by the Super Friends. In the comics, the main bad guy team is usually the Secret Society of Super-Villains. Other teams have existed, like Titans East, Injustice Society, Injustice Gang, Injustice League and Tartarus. Lex Luthor is usually included in teams that fight the Justice League/entire DC Universe, and often its prime member and leader.

They've fought alongside each other against plenty of alien invaders, not just Darkseid. Invasion!, Our Worlds at War and Blackest Night, for example. They even worked with Darkseid in Our Worlds at War and Cosmic Odyssey.