Naruto is a shonen franchise home to a wide cast of unique characters each with their own abilities, family histories, backstories, and motivations. However, with a cast so wide, it is inevitable that some get left on the cutting room floor. This is unfortunate as many characters of the famous manga had a lot of potential to be more than what they were left with.
Zetsu was a character introduced rather early on in the series as a member of the Akatsuki but later grew to be an essential part of the finale, granted one of the most unique and fascinating stories of the whole series.
10 He Could've Been The Only Spy In The Akatsuki
Zetsu's presence in the Akatsuki led to an air of mystery as the only member to work without a partner. Constantly going on espionage missions solo, Zetsu's appearance, mannerisms, and powers caused him to stand out from the rest of the organizations. However, once Tobi's identity is revealed, Zetsu falls into the background of the series and begins on a path that makes him less and less relevant until he's involved with Madara later on. If Zetsu was the only mysterious figure in the Akatsuki, he would have stood out more.
9 Black Zetsu's Heritage Could've Been Shown Sooner
It is recognized by many fans that the final chapters of Naruto feel rushed with rough pacing. However, this was later discovered to be Kishimoto wanting to finish the series due to the extreme pressures put on many mangaka. But the snippets of Black Zetsu's story that we gain in the final few chapters grant so much room to explore his background, motivations, and it forever changes everything known about the Naruto story. His origin as the manifestation of Princess Kaguya's will is extremely important to the series. Revealing this sooner could have made a smoother transition to discussing the Otsutsuki people.
8 He Could've Been A Villain Who Could Hold His Own
Zetsu's purpose in the story becomes muddled toward the end. He either serves Madara completely or betrays him to serve Kaguya, even stealing the position as the Sage of Six Paths for a time. However, he doesn't do anything unique that makes him stand out in the story.
Having him execute a plan that was his own, or something that kept him separate from Madara or Obito would have made him more memorable. Constantly copying other villains only to be overwritten a chapter or two later makes him seem more like filler than a unique character.
7 The Story Could Have Expanded On His Hokage DNA
White Zetsu holds the DNA of the First Hokage - Hashirama Senju. It would have been fun and interesting to see him use more of that incredible power throughout the story. Fans have already seen what a ninja can do with Hashirama's DNA through Yamato with his Wood release Jutsu. Seeing Zetsu use similar moves would have made his character more interesting and given his status as a clone—or a new creation as a human mutated by the Hokage's DNA—more presence in the series.
6 He Could've Been Used To Expand On Worldbuilding
Zetsu was originally a human who was captured within the God Tree by Princess Kaguya and then mutated by Madara's experimentation using Hashirama's DNA to recreate the tree. His perspective could have been used to expand on the lore of the Naruto mythos from a time before the warring states period, giving fans a glimpse of the reign of Princess Kaguya and the arrival of the Otsutsuki Clan. Zetsu's status as a prehistoric human makes him one of the most unique characters in the series and leaves so much room for development.
5 He Could've Been More Active In The Story
Zetsu spends the majority of the story watching and waiting in the background of important moments and reporting back to Madara. While this does make him mysterious initially, having it not amount to anything in the end can make a character forgettable. Nothing Zetsu does ever changes the dynamics of the story. If his action were to have lasting effects on the story and characters, he would have been more significant in the end. Giving him his own iconic fights and moments would have brought more substance to the character.
4 He Could've Spilled Some Secrets
Being allied with characters such as Obito, Madara and Itachi would give Zetsu access to a variety of forbidden information that would make him a dangerous enemy of the Naruto world and its leader.
If he were to release the true reason the Uchiha clan was wiped out, it would sow the distrust that Obito would have wanted and show the reader that he was an interesting character to follow. Constantly undermining the rule of the five Kage's by providing the public with the darker secrets of the world would leave them too busy to deal with Madara's plan.
3 He Could've Played A Role In Orochimaru's Inspiration
Although Orochimaru's origin isn't touched on very much besides his interest in researching forbidden techniques, using a character such as Zetsu, who would have been active during the Third Great Ninja War, would be an understandable trigger for his interest in cloning and human experimentation. Zetsu's link to the first Hokage would especially pique his interest and lead him to discover Jutsu such as the Edo Tensei. It would also show how he became obsessed with the Uchiha Clan and their abilities if he were to learn that Madara was still alive somewhere.
2 The White Zetsu Army Could've Had Unique Personalities
Madara having an army of White Zetsus from his original experiment in creating the God Tree makes sense for the story, each victim of Kaguya's reign sealed within and later mutated by Hashirama Senju's DNA. However, having each of them be the same person mentally does not make sense. If Hashirama's DNA or Kaguya's will corrupted them somehow, that form of power has never been shown to exist within Naruto. Though each could be loyal to Madara, it would make more sense for them to have unique personalities. It would definitely help White Zetsu stand out more if his personality was unique to him alone.
1 The Two Sides Of Zetsu Could've Had More Conflict With One Another
Both sides of Zetsu's identity showed different loyalties. Black Zetsu was loyal to Kaguya, while White Zetsu was loyal to Madara. However, throughout the story, neither of these loyalties comes into conflict. It could help to flesh out Zetsu's dual personality if they were to argue about who they'd rather follow. Black Zetsu could've revealed a separate agenda from White Zetsu and Madara, or Zetsu as a whole could've displayed some clear thought about betraying Madara or questioning his own motives. Another layer of personality to the character would create new and interesting roads to go down.