Thanos & Darkseid at a Glance
Darkseid: Darkseid is an evil ruler of the fiery hellish dark demonic volcanic desert and nightmare planet, Apokolips. He is an extradimensional being apart of the self proclaimed new gods who draw their power from another dimension. He has superhuman abilities and control over the Omega Effect, which allows him to project eye beams that can not only incinerate or teleport, but can also turn at right angles to catch their opponent. The Omega Beams, sometimes called Omega Sanction, lock onto the target's soul, preventing it from escaping. Wonder Woman's bracelets, along with Superman and Doomsday, are some of the only things to withstand a blast of his Omega Beams. Darkseid has a large set of other powers that make him nearly demonic and omnipotent. Darkseid is said to be hundreds of thousands of Earth years old, though Apokolips lives outside the normal boundaries of time and space in the DC Universe. Apokolips and the New Gods live across the DC Multiverse. Darkseid also has a whole army of other New Gods with the same attributes as his, (except for the Omega Beams) that he can call on for assistance. Darkseid is also the immortal-like demon God of Evil. He is fast enough to go from one end of the universe to the other in five seconds.
Thanos: In the Marvel universe, Thanos is a ruthless demon-like alien dictator from the moon Titan, who possesses many super powers and abilities, like a superhuman regeneration factor, teleportation, matter manipulation, darkness manipulation, and energy manipulation. He was formerly immortal because of Death's ban from her embrace.
Both Thanos and Darkseid contain a wide array of world-destroying abilities, but at the end of the day Darkseid reigns superior. Not only can his Omega Beams literally erase Thanos from existence before he'd even know what hit him (as Omega Beams function fast enough to catch speedsters), teleport him to any location (including the inside of a Quasar if he wanted), and disintegrate him on contact, but even his physicality alone would overwhelm Thanos (a lot argue that Darkseid has trouble fighting Superman as a way to measure how he'd fare with Thanos, yet in doing so disregard the fact that Superman is one of the most powerful beings in the multiverse and has only been vanquished by few, including Darkseid). When Darkseid has the anti-life-equation equipped and Thanos has the Infinity Gauntlet equipped, it is not a matter of power, but a matter of who strikes first.
Who’d Win: (without the anti-life equation + Thanos without the Infinity Gauntlet). Random selection (with the anti-life equation + Thanos with the Infinity Gauntlet)