2. The Wonder Man Controversy
When their rivalry was at its bitterest, Marvel and DC found ways to undermine each other creatively. In 1964, for instance, the House of M introduced a character called Wonder Man, which ticked its competitor off for obvious reasons.
Although DC didn't go running to the courts citing clear similarities to a certain Amazon warrior on its books, the publisher is said to have held crunch talks with Stan Lee and asked him to discontinue the offending superhero.
Not wishing to rattle any more cages, Lee obliged and Wonder Man was killed off. Characters rarely stay dead in comics, but this one might have if DC hadn't unveiled Power Girl just a few short years after Marvel introduced Power Man.
The then-Marvel editor is said to have been incensed that DC pulled the very same stunt they'd reprimanded his firm for years early. In an act of payback, Lee gave the green light for Wonder Man to be resurrected.