When you actually start breaking down the similarities between Xehanort and Thanos, things start getting kinda eerie.
1. Both Xehanort and Thanos wanted to bring balance to the universe by enacting a massive purge of life
2. Both Xehanort and Thanos adopted a young protege to train as an apprentice
3. Both Xehanort and Thanos are egoistical megalomaniacs with enormous savior complexes
4. Both Xehanort and Thanos have remarkably strong wills and convictions that sets them apart from the rest of the villains in their respective franchises (Thanos' convictions were the reason he was one of the few MCU villains to achieve his goals, and Xehanort's convictions were the main reason he was one of the only characters who could control darkness without being totally consumed by it)
5. Both Xehanort and Thanos were outcasts as children, Thanos because he was physically deformed and Xehanort because he literally grew up without a real home or family
6. Both characters get fought AFTER being killed once already
7. Both characters had to kill a person they loved to realize their ambitions (Thanos killing Gamora, Xehanort killing Eraqus)
8. Both Xehanort and Thanos achieved their goals before dying the first time, then were defeated in their second incarnation
9. They both have death scenes where they acquiesce to dying relatively peacefully
10. Both of them have a big, fancy sword
11. And, oh yeah, they're both bald