Darkseid

Lord Darkseid, once known as Uxas, is an ancient and all-powerful cosmic New God warlord and conqueror who reigns over the fiery, extra-dimensional planet of Apokolips and desires to rule the entire Multiverse, including Earth, by harnessing the unimaginable power of the Anti-Life Equation. He is the nephew of his former herald, General Steppenwolf.

Because of this tyrannical goal, he is the greatest arch-nemesis of the Justice League, the superheroic champions of the planet Earth, the only world that was able to resist his attempts at conquest.

Invasion of Earth
Thousands of years ago, before mighty Darkseid took The Throne of Apokolips, he became obsessed with the unholy Anti-Life Equation, a transcendental mathematical formula that eradicates free will. After locating the Equation on the planet Earth, he traveled there with an enormous army, planning to take the power of the Equation and use the seemingly weak world as a test run for his new power.

Upon arrival, he gained access to the Equation, and prepared to put it to use, but unfortunately for him, the native beings of that world, four powerful races known as Humans, Atlanteans, Amazons, and Old Gods, formed their own army to protect their world, even calling in help from the Green Lantern Corps in the form of Yalan Gur. In the battle that followed, Darkseid personally led the charge of his forces and easily slaughtered countless humans, Atlantans and Amazons and even managed to kill the Green Lantern Yalan Gur.

As he did so however, the Old Gods finally moved to meet Darkseid head-on. Artemis was the first to strike, shooting the warlord with two arrows which Darkseid quickly ripped out but he was immediately staggered further by a shockwave from Atlan's trident. Then Zeus, King of the Old Gods and leader of the Earth alliance, stepped in to confront the Apokoliptian warlord personally; blasting him with a barrage of divine lightning which Darkseid managed to block with his weapon but found himself locked in place. Spotting an opening, Zeus's son Ares sprinted forward, launched himself into the air with his axe poised over his head and came crashing down upon Darkseid, slicing through his opponent's weapon and cleaving open Darkseid's shoulder, forcing Darkseid to his knee. As the warlord bellowed with pain and rage, Ares furiously kicked him back several feet and moved to finish off the New God but was blocked by a contingent of Parademons, who dragged the severely weakened Darkseid back to the ship, forcing a retreat with his army, the Equation being taken from him as he did so along with the Mother Boxes being unintentionally being left behind in their haste. A furious Darkseid however was undeterred and vowed to claim the Equation again.

However, by the time he recovered from the nearly fatal injuries on Apokolips, the position of power he once held became almost nonexistent and the loss of Darkseid's influence ultimately resulted in a vicious war that by the time he came into a position of power once more, thousands of years had passed and those that had joined him on his failed crusade on Earth had all been wiped out. As a result, the exact location of Anti-Life and which planet that held it, and the whereabouts of the lost Mother Boxes, was forgotten by Darkseid, who after ascending as the ruler of Apokolips began a search that spanned thousands of years and the conquering of countless planets in order to find Anti-Life.

Refocusing on the terran populace
Millennia later, in 2015, the Mother Boxes begin to reawaken due to Superman's death, alerting his exiled general Steppenwolf. In 2017, while in the process of gathering the Boxes to create Unity, Steppenwolf rediscovered the Anti-Life Equation on Earth. Darkseid was later informed that Earth was not only the planet that held the Mother Boxes but also held the Anti-Life Equation he had failed to acquire.

Upon learning this, Darkseid ordered his uncle to prepare for his arrival and to terraform the planet with the Unity. He became stunned upon learning that Earth, the world which fought back, had the Anti-Life Equation for which he coveted, and promised his exiled minion his redemption in return for making ready the surroundings of his prize. While Steppenwolf managed to open a portal to summon Darkseid, he was defeated and slain by the Justice League before Darkseid could come across. He could only watch his enemies, lead by the Dark Knight, see that his three Mother Boxes on Earth were disabled.

An undeterred Darkseid resolved to come via "the old ways"; by direct warfare against Earth, tasking his servant DeSaad with preparing the Apokoliptian invading forces. Later on Earth, Martian Manhunterformally introduced himself to Batman, and warned that Darkseid was not through with Earth yet and that they need to find the Anti-Life Equation before he does.

Knightmare
In a possible future, after making it to Earth and tirelessly fighting the Justice League, Darkseid got his hands on the Anti-Life Equation again, and continued his conquest of the Multiverse. While fighting the League this time, Darkseid somehow killed Lois Lane (which Batman failed to prevent), which made a devastated Superman susceptible to Anti-Life. Soon after, Darkseid invaded Atlantis and killed Aquaman (and later presumably Wonder Woman as well), and made Superman ruler of Earth, transforming it into a hellscape wasteland. Darkseid tasked Superman with using the Regime to take down the Insurgency, the human/metahuman rebellion against the forces of Apokolips. The Insurgency fought well, but after years of fighting, most Insurgents were either converted to Parademons or were dead, and Batman, the Insurgency founder and leader, was killed by Superman, leaving only the Flash and Cyborg to stand against Darkseid.

Personality
Ever since he was raised on Apokolips, Darkseid has been famously known for his tremendous megalomania, seeing in himself as the true ruler of the entire Multiverse. Darkseid is therefore the ultimate walking power of malevolence, terror, and destruction, expressing his power over nearly all who dare face him. Indeed, even Wonder Woman showed fear when first learning of him.

Deeming himself as the one who turned thousands of planets into dust while looking for the one planet which has defeated him already, Darkseid is incredibly formidable and held great confidence in his abilities. This was evident during his past invasions where he personally led the charge against his enemies head on before his minions would. It is unknown if Darkseid still holds the same confidence in his battle prowess after his near death experience by the hands of Ares. Since his first defeat, he had began wearing body armor and even stopped personally leading invasions into other worlds.

Additionally, Darkseid is extremely obsessive and this prevents him from having any forbearance, especially with gaining his goals. Upon discovering the existence of the Anti-Life Equation, he developed a zealous obsession with it and sought to expend every resource at his disposal in order to acquire of this new power. He is also quite cunning and manipulative, knowing how to outsmart Superman into submission. This was seen in the Knightmare timeline, Darkseid has already conquered Earth with the Anti-Life Equation, as well as Superman himself (replacing the now-dead Steppenwolf with him). However, Darkseid seems to love his family to some degree, and didn't execute Steppenwolf but rather exiled him.