Kingdom Hearts vs Honkai Impact 3rd
Connection:
Both are major villains of famous video games who wore black coats and are known for their cunning and pragmatic schemes as well as being the final boss of their game's first part (Dark Seeker Saga and The Moon's Origin and Finality respectively) and being the dark reflection to the series' main protagonists (Sora and Kiana Kaslana respectively)
Both are old (Xehanort being 80 years and Kevin being 50,000+ years old)
Both originally started out as good guys, but had an experience that led them to the dark path (Xehanort became disillusioned that the worlds must be purged so that light and darkness are balanced, whereas Kevin witness his world being ravaged by the Honkai and the death of his lover Dr. MEI which made him more cynical and bitter)
Both seek to change the universe which involves harming the innocent (Xehanort wants to bring balance between light and darkness by conquering Kingdom Hearts and remaking worlds in his own image. Kevin wants to initiate Project STIGMA, which will cause 99% of humanity to die so that the few who survive who develop Stigmatas) but both would be confronted by their former friend (Master Eraqus and Su respectively)
Both wield giant swords (No Name and Judgement of Shamash respectively) and are the leaders of an evil organization (Organization XIII and World Serpent respectively)
Both have even manipulated one of the heroes (Xehanort tricking Terra into giving in to the darkness to which he stole Terra's body, whereas Kevin makes Raiden Mei join World Serpent in exchange for them saving Kiana's life) but said heroes would return to the light (Terra regains his body and Mei rejoins with Kiana)
In the climax of their stories, both would gain absolute power (The true Kingdom Hearts and Authority of Finality respectively), possess new swords (The X-Blade and Might of An-Utu respectively) and an all-new monstrous form (Armored Xehanort and Deliverance Kevin respectively)
Both are confronted and ultimately be defeated by an iconic trio of heroes of their respective series (Sora, Donald and Goofy for Xehanort. Kiana Kaslana, Raiden Mei and Bronya Zaychik for Kevin). Afterwards, both accepted their defeat and handed the power they have to the main heroes, entrusting them to protect the universe and future before dying and passing on (Eraqus and Xehanort departed to the afterlife together, while Kevin was reunited with MEI and the other Thirteen Flame-Chasers)
