Thanos' Deepest Secret Explains Every Contradiction in His Character
Warning: Contains minor spoilers for Eternals #10
The Mad Titan Thanos is a contradicting character, with different personalities apparently locked in endless conflict. The key to understanding the true nature of Thanos, however, might come from his most recent enemies, the Eternals.
When Thanos was created by Jim Starlin, he was defined by his nihilism and worship for Death: amongst a host of villains who wanted to conquer the world or the universe, he instead wanted only to destroy. Thanos was also a mix of cunning and brute force. After the Infinity Gauntlet saga, however, Starlin decided that Thanos had been a villain long enough. After all, he obtained his goal, gaining ultimate power and offering half the universe as a tribute to his love, Mistress Death. When he did, however, he found out that his quest had been futile: to do what he was asked to do, he had to become so powerful that even Death was no more than his servant, and she could not give him the love that he craved. So Thanos "retired", and even helped the heroes in saving the universe more than once, but such a charismatic villain could not be redeemed for long.
After Starlin stepped away from Marvel, Thanos was back to villainy. He was a cosmic serial killer, a psychopath bent on destruction and depravity, but whenever Starlin periodically came back to Marvel, he'd turn Thanos back into a philosopher whose nihilism is balanced by an endless thirst for knowledge. This created some contradictions at first, to the point that Starlin wrote a whole series only to use clones to retcon what other writers had done to Thanos. In the long run, however, Thanos' conflicting traits became a key aspect of his personality, albeit sometimes hard to explain. One comment in Eternals #10 - by Kieron Gillen, Esad Ribic, and Matthew Wilson - can finally help in doing just that.
Thanos recently became Eternal Prime, the leader of the Earth Eternals, and he is using the power and knowledge coming from that position for his nefarious plots. These include the torture of the inventor Phastos to make him share his secrets, but the commentary by the Great Machine (the artificial intelligence that serves the Eternals and is narrating the story in the comic book) reveals something more. "Thanos is a monster", it says, "but he is also playing the part of a monster. He is aware he must project callousness, but he is frustrated. This sadism brings him no closer to his goal." This suggests that much of Thanos' worst excesses are a form of performance - things he does so he will be feared and obeyed, and yet not things he particularly enjoys. Thus, Thanos' more contemplative side - which includes affection for people like Gamora or Adam Warlock - is his true self, while his most sadistic moments are partly a performance to stoke his legacy and get him what he wants.
This interpretation has the merit of marrying the disparate depictions of the characters, explaining how the reclusive scientist who saved the universe many times is also the sadistic serial killer who is addicted to death and fathered countless children across the galaxy as a (failed) experiment in feeling love. Originally, Thanos' love for Death was an extension of his true nihilist spirit, which considers life devoid of purpose. He could be somehow stuck in that portrayal of himself, despite having already philosophically outgrown those tendencies, but still using the fear that his sadistic exploits bring into people to obtain his goals. Regardless of what the truth is, or perhaps because of these contradictions, Thanos remains Marvel's most fascinating villain.