Killer B's Jinchūriki Forms

Kirābī is a Jinchūriki of the Eight-Tailed Beast, and is therefore capable of transforming into various forms that resembles his Tailed Beast, until he finally takes on the complete form of the Eight-Tails. So far, he has only displayed two forms. Unlike Naruto and Gaara, he seems to have full control of the Eight-Tails and his transformations. According to some Kumogakure shinobi who passed by and saw his full transformation, the Raikage had forbidden him to transform.

Three-Tailed Transformation
When need be, Kirābī will tap into the Eight-Tails’ chakra and generate a demon cloak similar in appearance to Naruto’s One-Tailed Transformation (and onwards).

In this form, his incisors grow long and sharp and Kirābī is covered in a boiling chakra shield, that takes the shape of his Tailed Beast by forming three tentacle-like tails on his behind, and paws of chakra around his hand. However, instead of just creating fox-like ears like Naruto's demon fox cloak, his chakra cloak has formed a pair of bull-like horns. Due to Kirābī's great control of the Eight-Tails, this transformation can be done instantly.

In this form, he becomes powerful enough to blow away Sasuke's entire neck and chest, but also begins to move in a straight line, something Sasuke noted to be a weakness. However, Kirābī simply retorted that Sasuke would not be able to keep up.

Full Transformation
While fighting Sasuke and his team, Kirābī managed to wound Sasuke long enough to transform into the Eight-Tails' full form.

In this form, he takes on the appearance of the Eight-Tails itself, rather than just a cloak, appearing like a huge ox with eight octopus-like tentacles as its tails and four horns on his head, though with one of them broken. Like with his previous form, he seems to be in full control of this form, however to what extent is still unknown.

In this form, he seems to be able to create a black sphere of energy in front of his mouth and then shoot it out as a massive blast of energy. This attack is very similar to Naruto's Four-Tailed Strong Ball, but with more power.