Killer B's Jinchūriki Forms

Killer Bee is the jinchūriki of the Eight-Tailed Giant Ox, 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 three 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.

One-Tailed Transformation
After Kisame used Samehada to take the chakra of Killer Bee's Eight-Tailed cloak, Killer Bee was left in a one-tailed form.

Three-Tailed Transformation
When need be, Killer Bee will tap into the Eight-Tails' chakra and generate a demon cloak that takes the shape of his Tailed Beast by forming three tentacle-like tails on his back, and paws of chakra around his hands. In this form, his incisors and nails grow long and sharp. Due to Killer Bee's great control of the Eight-Tails, this transformation can be done instantly.

In this form, he has increased strength and speed, though Sasuke was still able to keep up using his Sharingan. Additionally, he can form the chakra cloak into bull-like horns and use them in a powerful strike, at one point blowing away Sasuke's entire neck and chest. However, unlike Naruto's three-tail transformation, Killer Bee's attacks in this form are straightforward.

Four-Tailed Transformation
During his fight with Kisame Hoshigaki, Killer Bee went straight to his four-tailed transformation in a similar manner similar to his three-tailed shroud. Though the form was very brief, due to Samehada absorbing his chakra, though it varied greatly from Naruto Uzumaki's four-tailed transformation in that Killer Bee's fourth tail doesn't warp his body at all, it simply adds another tail.

Seven-Tailed Transformation
As his fight with Kisame continued, Killer Bee quickly grew seven tails for his chakra shroud, which like the four-tailed form, only grew an extra tail, but greatly increased his power. However due to Samehada eating his chakra, this form two was not able to effectively damage Kisame.

Version 2
To give himself an edge without resorting to his full transformation in fear of hurting Sabu and Ponta, Killer Bee asked for enough chakra from the Eight-Tails to a warped version of the previous seven-tailed form. This seven-tailed version is similar to Naruto's six-tailed form, in that the chakra warps his body into a solid chakra shroud. Killer Bee can form similar bones from the chakra to use for combat.

Eight-Tailed Transformation
After his seven-tailed form's chakra was eaten by Samehada, Killer Bee's chakra shroud returned to the basic form, albeit with eight-tails as opposed to seven. Because this slipped into this form as a result of having his chakra eaten in the Version 2 form, it can be assumed this form, despite having eight tails, is weaker than Version 2 of the seven-tailed form.

Full Eight-Tailed Transformation
While fighting Sasuke and his team, Killer Bee managed to wound Sasuke long enough to transform into the Eight-Tails' full form, in which his skin is destroyed in a similar fashion of Naruto when he reaches the fourth tail and above. In this form, he takes on the appearance of the Eight-Tails itself, rather than just a cloak, appearing like a huge ox-like creature with eight octopus tentacles as its tails and four horns on his head, one of which is broken. Like with his previous transformations, he seems to be in full control of this form, though to what extent is still unknown.

In this form, he is able to create a huge sphere of chakra in front of his mouth similar to Naruto's Four-Tailed Fox Menacing Ball, but he releases it as a widespread blast instead of a concentrated ball, and it is on a far larger scale due to Killer Bee being completely transformed. However, even in his full form, he does not possess an invincible shroud like the Nine-Tails, so even with his immense size, powerful attacks such as Chidori and Amaterasu will still be effective.

Trivia

 * When Killer Bee is first seen entering a three-tailed form, his chakra shroud envelops his scarf and belt. This does not occur when he later assumes a four-tailed transformation.