So the outline I have for my story is that the hero has amnesia due to the plot of the villain to kill him but he doesn't know that but eventually does since the villain figured out he was still alive and plotted against him again which is leading him down to this journey to remember who he once was then, a couple of scenes later, he gets to remember everything (there's character growth and character development)just before he's gonna defeat the main villain and once he defeated the villain, I want to initially show the epilogue of the hero's life but my question is: Is it fine to end it there when in the entire story, his goal was to defeat one villain because I only have read novels where after who we thought was the main villain was nothing in compared to the next villain.
Of course. For novels of feature length films, one villain is usually enough, provided that you have dedicated enough paragraphs to the one villain.
In series (TV or book) however, authors have an interest in continuously "upping the ante" on "villainness", because it gives the writer more room for extra episodes, seasons, or books. But many stories that I know of, especially shorter narratives, have only one main villain, and the hero's journey leads them to confront them, which resolves many plot points. And if it doesn't, then instead of an epilogue, I would continue narrating to resolve any other themes that you have written: Interesting stories come from an inner conflict, and not an external one.