A complex antagonist who moved well beyond the shadowy, one-dimensional villain of his early big-screen appearances, Thanos had a massive impact on the Marvel Cinematic Universe, and on audiences. The Mad Titan's analog in the DC Universe is traditionally viewed as Darkseid -- after all, Thanos was modeled on the iron-fisted ruler of Apokolips. However, as the animated Justice League and Young Justice adaptations have demonstrated, it is Vandal Savage, not Darkseid, who's the most compelling counterpart to Thanos and, therefore, deserving of more attention on the big screen.
Thanos has well-defined, even admirable, qualities, like a moral code, as twisted as it may be. His actions in the MCU -- namely, assembling the Infinity Stones to bring "balance" to the universe by snuffing out half of all life -- are informed by a distorted philosophy that makes sense to him. He's not fueled by blind hatred or malice, but instead by a perverted sense of justice and care for the universe.
Those qualities are what make great villains in fiction: characters who possess noble traits but are tragically destined because their flaws make them do unconscionable things. Being evil isn't enough to be compelling; it's the antagonist's depth -- his humanity -- that makes the character interesting. Obviously, Marvel Studios did a solid job of developing Thanos.
Unfortunately, Darkseid seldom displays the same capacity for such depth. He's practically an incarnation of dominating evil, embodying it to a near-literal level. Giving him a softer, human side would contradict his core character. Darkseid is inhuman by design, in both motives and methods.
Unlike the MCU's Thanos, who seeks to save the universe, in his own way, Darkseid's goal is to find the Anti-Life Equation so he can end everything that humans consider to be life. As ruler of Apokolips, he lords over a hellscape of torture and misery. There's nothing for audiences to empathize with for what amounts to be a stand-in for the devil. He purposely lacks human qualities, so making him into a sympathetic, or even understandable, character is quite likely an insurmountable challenge.
The immortal Vandal Savage, on the other hand, has been shown repeatedly to have a complex personality, capable of self-reflection, growth, and even remorse. He's human in a way Darkseid can never be. In the animated Justice League episode "Hereafter," Superman meets a Vandal Savage from a dystopian future, in which he has practically destroyed the world -- the goal of many supervillains. Rather than gloating, however, Savage is contemplative and remorseful, understanding the weight of his actions. His immortality has bolstered his humanity, and he ultimately assumes the role of hero to help set things right.
The Vandal Savage portrayed in Young Justice is perhaps even more compelling and complex. Early in the running of the animated series, he comes across as a manipulative man who always seems to have a secret up his sleeve. Clearly, he's with the bad guys, but the show doesn't stop there with his characterization. He's calm, cool and collected, but he's not above admitting his mistakes. In "Summit," Savage concedes he has underestimated the younger heroes, but he will not do so again.
His goal on Young Justice is not merely to take over the world, but to save it and lead humanity to a brighter future. As the show's backstory continues to reveal in "Evolution," Savage has long acted as a brutal, if not effective, protector of humanity against alien threats. His methods are certainly not in line with the heroes, but his goals are admirable.
Savage is also similar to Thanos in that he's not above committing atrocious acts to further his goals. However, much like the Mad Titan, that doesn't mean Savage can't feel the emotional weight of his actions. In Infinity War, Thanos sacrifices his adopted daughter Gamora to gain the Soul Stone; on Young Justice, Vandal similarly kills his own daughter, who has become senile, and a liability. But even in that dark moment, Savage is shown to have compassion, and his murderous act can even be interpreted as a twisted mercy killing.
DC and Warner Bros. should take notes from Young Justice when it comes to establishing a captivating and well-rounded villain for their superhero film franchise. While Darkseid is indeed formidable, Savage has proved he can also be an intimidating threat who operates on a planetary scale. Using the wit and wisdom gained from countless lifetimes, he is capable enough to take control of Warworld, a weapon capable of destroying entire planets.
And unlike Darkseid, he is capable of those feats while still maintaining a tether to his humanity, making him a far more compelling antagonist.