(or "From Jesus Christ to Nietzsche In One Book")
Sometimes, it's the B and C-list characters at Marvel and DC that can be the most interesting. Spider-Man's storytelling engine was established early, and was such a profound success that nobody has dared to tinker with it overmuch. (At least, not on a permanent basis. Lots of people have made big changes, but somehow a few years after they announce that the series will permanently be the adventures of a Starbucks barista named Ben Reilly, we're right back to Peter Parker, hard-luck hero.)
But a character who's hovering on the edges of success, like Spider-Woman or Killraven or Adam Warlock, is constantly being reinvented in an effort to find a recipe that works. Each new writer that comes in rarely feels beholden to the ones that came before, so Spider-Woman can suddenly become a bounty hunter, or Killraven can shift in tone from pulp-inspired action-fest to introspective satire of pop culture...and Adam Warlock, whose story started as a sci-fi reworking of the Gospels, became an exploration of Nietzschean philosophy with a time travel twist.
Originally, of course, Adam Warlock started as Him, a minor Fantastic Four villain in the "more confused than evil" vein who also duked it out with Thor once or twice. But when Roy Thomas decided to turn the character into a hero, it was in the midst of a strange zeitgeist where the counter-culture of the Sixties and Seventies played up the anti-establishment aspects of Jesus' life and message. It was a time when Jesus was seen by some as the ultimate hippie, and even as the religious establishment aligned itself further right, the Bible was tremendously relevant to America's youth. Reinterpretations of the gospel stories that appealed to this cultural movement, like 'Jesus Christ Superstar', were tremendously popular...and so, Thomas thought, why not do the same thing with superheroes and science fiction?
And so another minor villain, the High Evolutionary, was drafted into service as the new Yahweh of this Marvel Universe version of Genesis. Within the span of a few pages, he created Counter-Earth, and his rebellious Ani-Men played the part of Satan and his minions. Adam Warlock, natch, was Jesus, sent down by his stern yet loving father-figure to teach counter-humanity a better way of living in the face of the persecution of the Man-Beast, and to avert the Counter-Apocalypse.
It was a magnificently clever conceit that produced a run of strong stories, but as a storytelling engine, it was limited. There were only so many times that Adam Warlock could plead with the High Evolutionary not to destroy the counter-human race before it got repetitive, and only so many times that Warlock could foil the Man-Beast before it became obvious that a grand final confrontation was needed. A confrontation that we got, in suitably apocalyptic fashion, but one that left the series and the character at loose ends.
Later, Warlock was brought back by Jim Starlin, who had already developed a habit of creating a personal mythos that followed him from title to title. This saga followed Thanos, a mad demigod who believed it to be his duty to bring death and destruction to the universe as the servant of Death herself, whom he loved, and various heroes who challenged Thanos and his army of mercenaries as the villain grew in power from appearance to appearance. The mythos truly began to solidify, though, when Starlin found in Warlock a hero whose thematic opposition to Thanos gave him a means to create a moody, introspective, philosophical work as well as a cosmic action epic.
In Starlin's cosmology, Warlock was the polar opposite of Thanos, a life-force to counter Thanos' death-urge. At the same time, Warlock also represented the ubermensch, as his origin (way back in Fantastic Four, in case you forgot) was an attempt to create a perfect form of life. These two are presented as merely one recurrence of an eternal struggle that has gone on throughout time, with all existence merely being the result of that struggle.
But Starlin has a particularly Nietzschean trick up his sleeve, one that drives the majority of his first great Warlock story. Warlock is the life-urge, but that doesn't necessarily mean anything as simplistic as him being "good". The other main villain of the Warlock saga, the Magus, is the Dionysian counterpart to Warlock's Apollonian hero, a version of himself from the future who has imposed a crushing tyranny onto the galaxy. It's an empire devoted to peace and prosperity and the extinguishing of Thanos' death-urge, but at the cost of all freedom. When Thanos manipulates Warlock into fighting the Magus, we can sympathize with Adam even though he's defeating the one person who may be able to stop the mad god.
Like the previous saga, though, Starlin's Warlock had its limits as a storytelling engine. And Starlin made it very clear that he knew it, by concluding the Magus saga with Warlock killing his own future self to prevent him from becoming the Magus. He then wrapped up the battle with Thanos in a grand epic that featured the Avengers, Spider-Man, and Warlock's death at his own past self's hands...in a way that took Thanos with him, of course.
Starlin eventually did return to the character (in stories that fall outside the scope of the first Essential Warlock collection.) When he did, he was careful to create a more open-ended concept of Warlock, one that retained the philosophical bent while avoiding the limitations of the pure dualism that characterized his earlier works. But it remains amazing just how much fertile soil was found in a character that never reached great heights of popularity...but whose engines created some of the most classic and enduring stories Marvel ever told.