Surprisingly, Marvel and Star Wars actually agree on whether Thanos or Darth Vader is the most powerful being. Serving as major antagonists in their respective universes, the Mad Titan and Dark Lord of the Sith are both incredibly significant villains in pop culture. Both are equally compelling and dynamic characters as well. However, one writer has definitively confirmed which of the two is the most effective.
In 2015's canonical Darth Vader series, the 17th issue featured Darth Vader's ongoing rivalry with Grand General Tagge. Being promoted by the Emperor in direct response to Vader's failure to protect the first Death Star, Tagge boldly carried little respect for the Dark Lord. To that end, the issue uses Tagge to evaluate Darth Vader's methods in his service to the Empire. Despite his concession that Vader is a great warrior, Tagge claims being great is not enough: "Vader wins grand victories in the same amount of time I win a thousand small ones. He can win battles, not wars.".
Remarkably, this sentiment in a galaxy far, far away is strikingly similar to a line about Thanos shared by his brother Eros in Marvel's recent AXE: Starfox #1. Reflecting on his years fighting the Mad Titans with love while Thanos exists as an avatar of death, Eros concedes that while he can win battles, "Thanos wins wars". Not only is Thanos' effectiveness evaluated with the same language as Darth Vader, it's not exactly a coincidence either as both issues were written by Kieron Gillen.
Darth Vader Wins Battles While Thanos Wins Wars
This concept presented by Gillen across universes is quite accurate. When looking at their respective accomplishments, Vader is indeed a great warrior and is extremely powerful wielding the dark side of the Force. However, Vader still served and answered to Emperor Palpatine at the end of the day. In contrast, Thanos has held the universe in the palm of his hand on several occasions thanks to the Infinity Stones and other great powers such as the Uni-Mind which recently made him the Prime Eternal. Furthermore, he answers only to the personification of Death itself.
Given the years between these comics' publications, it's hard to tell if Gillen built this argument intentionally or not. Regardless, the core concept is still true. Thanos wields more power and authority than Darth Vader, existing as a stronger and more capable villain overall. AXE: Starfox #1 is on sale now.