Saigo no Getsuga Tenshō

is a technique of Ichigo Kurosaki's Bankai, Tensa Zangetsu.

Description
By using this technique, Ichigo becomes itself. It is referred to as the “Final” Getsuga Tenshō because if Ichigo uses it, he loses all of his Shinigami powers. For the duration of the ability, Ichigo's hair turns black and becomes waist-length. A bluish-gray bandage-like carapace forms around his torso, right arm, and face, ending just beneath his eyes. Black, flame-like markings spread across his chest and wrap around his left arm, and the remains of a tattered black cloak cover his lower body. In this form, Ichigo's body constantly emits smoky black reiatsu, most of which is focused around his right arm. Being in this form allows Ichigo to use Mugetsu. Once it is used, the transformation dissipates. Afterwards, he will lose consciousness, accompanied by intense pain, with the loss of his Shinigami powers following. Any remaining reiryoku will stabilize, and he will awaken some time later (roughly a month), followed shortly by the loss of his remaining reiryoku. However, when Ichigo lost his reiryoku, a tiny portion of it accumulated in a single location inside of him over time, and he began to regain it slightly after a year and a half.


 * Ichigo, generating a blade of deep black reiatsu in his hand, swings it towards the target. Doing so causes a massive veil of reiatsu to erupt upwards and approach the target, darkening the sky and heavily damaging anything caught within the blast. The energy, continuing to rise, dissipates into the sky. The technique is strong enough to severely damage Aizen in his strongest evolutionary stage and force him to regenerate at a previous stage.