Combat Bleach is largely based around the soul-cutting swords, Zanpakuto. These are the blades carried by Soul Reapers like Rukia Kuchiki and series protagonist Ichigo Kurosaki, who has a Zanpakuto of his own. Early on, Ichigo met his match against Renji Abarai, who wielded a Zanpakuto named Zabimaru.
At the time, Renji and his Zanpakuto were a real threat, but before too long, Bleach scaled up and battles became bigger, more complex — and Zabimaru was largely left in the dust. But it still served a significant purpose.
Abarai's Zabimaru Introduced Viewers to Combat Concepts
Near the end of Bleach's first season, Rukia was found guilty of serious crimes, and her elder brother Byakuya Kuchiki was (at the time) stubbornly fixated on law and protocol. He sent his Lieutenant, Renji, to capture Rukia and defeat anyone who got in the way, meaning Renji and Ichigo came to blows. Despite being a novice with an unnamed Zanpakuto, Ichigo fought back well, so Renji performed the first onscreen Shikai, morphing Zabimaru into a bigger, segmented blade. This was a rather basic but effective Shikai transformation, and with it, Renji broke even against Ichigo. Renji stood down when Byakuya himself arrived to handle matters, and Renji returned to Soul Society with the Kuchiki siblings.
Renji fought Ichigo again during the Soul Society invasion arc, and this time, he suffered a narrow but definite loss against Ichigo, even when using the full power of Zabimaru's Shikai. By this point, Renji was convinced to take Ichigo's side and protest Rukia's execution, coming to blows against his own Captain sometime later. This was when Renji performed his Bankai for the first time, Hihio Zabimaru, though he soundly lost to Byakuya in this futile match. Renji later faced the traitorous Sosuke Aizen with Ichigo, and was once again soundly defeated by a Captain.
In later arcs, Renji faced and defeated a Fracción named Ilfort Grantz, a minion of Grimmjow Jaegerjaques'. During the Hueco Mundo invasion arc, Renji faced the Espada Szayelaporro Grantz and fought well with Uryu, but they were nearly defeated until Captain Mayuri Kurotsuchi joined them and defeated the Espada. Renji, Chad and Rukia helped fend off the Exequias soon after that, buying Ichigo time to go after Ulquiorra Schiffer. Renji's final major fight was against the Sternritter called Mask de Masculine, using his newly-transformed Bankai to defeat this brutish Quincy and save Captain Otoribashi from certain death. Overall, Renji has had his fair share of scraps with Zabimaru in hand, but the conclusion to be drawn about Zabimaru's performance is a mixed one.
Zabimaru Is a Basic, But Essential Zanpakuto
Overall, as far as Zanpakuto go, Zabimaru is among the least flashy and unique of them all, especially in Shikai state, but that isn't necessarily a huge weakness on its part. Zabiumaru was an introduction to the concept of Shikai and Bankai for the viewers, and its simple but eye-catching Shikai provided an appropriate challenge for Ichigo when it first appeared. Szayelaporro himself noted that Zabumaru is a rather straightforward, even boring, Zanpakuto, but that's just what Bleach needed at the time, and Ichigo would have stood no chance against a tricky, Kido-based Zanpakuto like Sode no Shirayuki's Shikai or Captain Soi Fon's Suzumebachi Shikai.
The power levels and complexity of Zanpakuto gradually scaled up as Bleach progressed, and Zabimaru helped ease viewers and Ichigo alike into the world of Shikai with its basic but effective forms and abilities.
What's more, Zabimaru was roughly keeping pace with Zangetsu, Ichigo's own Zanpakuto, reinforcing Renji as Ichigo's friendly rival. Zabimaru was a basic Zanpakuto to match Zangetsu at the time, and Renji's Shikai challenged Ichigo to improve himself as a fighter and unlock the next step in Zangetsu's evolution (which indeed happened when Ichigo trained with Kisuke Urahara). Then Zabimaru set another high bar by achieving a flashy Bankai while fighting Byakuya, and Ichigo kept pace with his own Bankai, Tensa Zangetsu.
Later still, both Ichigo and Renji suffered serious defeats at the hands of the Sternritter, and they both met the Captains of squad 0 to reassess their relationships with their Zanpakuto and re-forge them into their ultimate selves. Zangetsu and Zabimaru alike were reborn, and Ichigo and Renji charged into battle with renewed strength and conviction. And even if Zabimaru is pretty basic, it (and its owner) had the strength and willpower to face a mighty Sternritter and win, avenging Renji's quick defeat at the hands of Mask de Masculine earlier in that story arc. Like Zangetsu, Zabimaru knows no limits.
