So... is Needless finished or not?
NO, it is not finished.
Why?
The anime finished before the manga:
Anime finished: December 11, 2009
Manga finished: June 19, 2013
MangaUpdates contains information about the anime adaptation and indicates that it is incomplete.
Watching Order (by release date)
Here you have all the anime relations we detected ordered by release date, so you can see the reason for this status in context and also use it as watching order.
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Synopsis
Needless takes place in a post-apocalyptic Japan, fifty years after World War III. Mysterious contaminated zones called "Blackspots" have appeared, isolating communities and causing some people to develop extraordinary abilities, becoming known as the Needless.
The story follows Adam Blade, a powerful Needless with incredible regeneration and strength. He's determined to bring order to this chaotic world.
Together with his allies, Adam must confront and overcome the sinister Simeon group, which seems to be a major source of conflict and unrest in this war-ravaged landscape. Their struggle is about survival and reclaiming peace in a fractured society.