In the Naruto universe:
* Chakra reserves: Kurama is known for its vast chakra reserves, being one of the strongest tailed beasts. However, the Ten-Tails possesses even greater power and chakra, making it stronger in this aspect.
* Physical strength: While Kurama is incredibly strong, it's debatable if it's the strongest physically. Other Tailed Beasts like the Eight-Tails, with its chakra arms, could potentially be considered stronger.
* Combat abilities: Kurama's power and versatility in combat are undeniable. However, individuals like Madara Uchiha, who mastered the Rinnegan and could control the Ten-Tails, could potentially be considered stronger in combat.
* Wisdom and experience: Kurama is wise and experienced, but it's not necessarily the wisest or most experienced being in the Naruto universe. Others, like the Sage of Six Paths, could be considered more knowledgeable and skilled.
Outside the Naruto universe:
* Gods and deities: Many myths and legends feature powerful deities and gods who are vastly stronger than any fictional creature, including the Nine-Tailed Fox.
* Abstract beings: Beings like the concept of "time" or "death" often hold immense power that transcends physical limitations.
* Cosmic entities: Some fictional universes feature beings with powers that operate on a cosmic scale, far surpassing any individual creature's strength.
Ultimately, "stronger" is subjective and depends on what criteria you use to define it. The Nine-Tailed Fox is incredibly powerful within the Naruto universe, but there are definitely other beings, both within and outside its fictional world, who could be considered stronger in various ways.