In the Naruto anime and manga series, there are several powerful swords, each with its own unique abilities and characteristics. While the concept of "strength" can be subjective and dependent on various factors, including the wielder's skills and the context of the story, one sword is often regarded as particularly strong:

Kubikiribōchō (also known as the Executioner's Blade or Decapitating Carving Knife) is often considered one of the strongest swords in the Naruto universe. It is wielded by the character Zabuza Momochi. Kubikiribōchō has a massive, wide blade with a serrated edge and a curved hook at the tip.

What makes Kubikiribōchō unique is its regenerative abilities. The sword has the ability to heal itself by absorbing the blood of those it cuts. This regenerative property makes it incredibly durable and difficult to damage or break in battle. It is also said that Kubikiribōchō is strong enough to cut through almost anything, including iron and stone.

Furthermore, Kubikiribōchō can be disassembled into several separate blades, transforming it into a more versatile weapon. Zabuza often utilizes this feature to surprise and overwhelm his opponents.

While Kubikiribōchō is known for its strength and regenerative abilities, it's important to remember that strength in the Naruto universe is not solely determined by the weapon itself but also by the skills and techniques of the wielder.