Superman is at the center of Justice League's best episodes
"Hereafter" was, like most episodes of Justice League, a two-part episode. It explores the idea of Superman dying, and how the world would be without a Superman.
The first part of "Hereafter" begins with a revenge squad of villains, all bent on destroying Superman. They battle the Justice League, until one villain, The Toyman, is able to kill Superman with a Kryptonite ray. Superman is in actuality sent to a future where another long time villain, Vandal Savage, is the last surviving person on Earth.
The Justice League has to face a world without a Superman, and it is rough. Villains go on rampages, because, without a Superman, there is less chance of them being stopped. Fan favorite villain Lobo arrives and joins the Justice League, although without the League wanting him to.
Lobo's presence goes a long way in "Hereafter". For an episode of Justice League, there is certainly an air of sadness to it, with everybody presuming Superman is dead. Lobo is a funny character, one of DC's most comedic villains, or antiheroes, in this case. Him fighting alongside the Justice League is an amazing spectacle, as he defeats villains in the least heroic ways possible.
Superman finds himself against Vandal Savage, an old foe, who he has no reason to trust. Vandal Savage reveals that it was he who destroyed the Earth, 30,000 years ago, because Superman wasn't there to stop him. He then requests that Superman helps him get access to a time machine, and that he goes back in time to defeat himself before he causes the destruction. When Superman does return to the past, he and Vandal Savage part as friends, knowing that the next time they meet, they will be enemies.
"Hereafter" is a great two-part episode, it asks questions about the DC universe, and about the importance of Superman. It is also about a man who comes to regret what he has done, and does all he can to set things right, going so far as to ally with one of his oldest foes.
"Hereafter" has earned a place in the hearts of fans, forever. And it has withstood the test of time as one of the animated series' very best installments.