Kinshiki Ōtsutsuki

was a member of the Ōtsutsuki clan, who served his son Momoshiki.

Background
At some point, Kinshiki consumed his guardian's chakra after they entrusted him with their power. His and Momoshiki's actions earned them Kaguya Ōtsutsuki's wariness, believing them to one day come to steal her chakra.

Personality
Kinshiki was very loyal to Momoshiki and was also a father figure to him, to the extent that he offered himself to be changed into a chakra pill. Kinshiki also showed a vengeful side, as he was determined to kill Sasuke for cutting his horn off from their first battle. Like Momoshiki, he has no regard for others, other than for Momoshiki; this is seen when he tried to kill Sasuke Uchiha as he was trying to get his daughter to safety in the middle of the chaos Momoshiki and Kinshiki brought upon their arrival to Konoha.

Appearance
Kinshiki had pale skin with short spiky blue-greyish hair, a full beard, and a long horn above his left eye that was later stubbed by Sasuke Uchiha. He had big hands and a burly physique accompanied with a towering height that reached over two metres.

He wore a pale blue shirt with back cuffs and a high collar over which he wore another darker appendage with a grey sash wrapped around his waist. He also wore grey pants and black, flat shoes on his feet which were upturned at the toes.

Abilities
Kinshiki was an extraordinarily powerful being who, alongside Momoshiki, was deemed a threat greater than Kaguya, the progenitor of chakra. He was capable of holding his own against multiple Kage-level opponents at the same time, and restraining a perfect jinchūriki. As an Ōtsutsuki, Kinshiki possessed extremely powerful chakra and was capable of flight. He showed the ability to create various red glowing ninja tools at will, which he was proficient with handling. He could also sense chakra, being able to locate fragments of Kaguya's across countries.

Physical Prowess
As evident from his enormous size, Kinshiki possessed incredible strength and durability, as he could escape being confined and immobilised by two Kage. Despite being on the verge of death, he could cut down his own planet's God Tree with a single slash of his halberd. Kinshiki was proficient in close-range combat and showed deceptive speed, being able to fight on par with Sasuke Uchiha.

Byakugan
Kinshiki posessed the Byakugan, granting him a near 360° field of x-ray vision (with the presumed exception of a small blind spot at the upper thoracic vertebrae), and the ability to see the chakra pathway system.

Boruto: Naruto the Movie
Kinshiki and Momoshiki encountered Sasuke, who had been travelling through another dimension to gather information on a threat greater than Kaguya Ōtsutsuki. In a blizzard of another dimension, Kinshiki engaged in battle with his kanabō against Sasuke and his sword. Sasuke was nearly overpowered by Kinshiki's monstrous strength and barely escapes with his life.

Kinshiki and Momoshiki sense Kurama's chakra in the ninja dimension and intended to capture Kurama by kidnapping its' current jinchūriki, Naruto Uzumaki. They appeared during the Chūnin Exams in Konohagakure and started creating chaos. Kinshiki destroyed the arena and attempted to attack Sasuke and his daughter. Shikamaru Nara uses his Shadow Sewing Technique to restrain Kinshiki and Momoshiki, but Momoshiki absorbs his power. After Momoshiki explained their goal to gather Kaguya's scattered chakra and cultivate it into a new 'cinnabar panacea' in order to gain eternal youth and supernatural powers, Kinshiki fought Naruto and Sasuke, who combined Kurama and Susanoo to shield themselves. However, Kinshiki and Momoshiki successfully captured Naruto when he allowed himself to be caught in their technique to protect his son, Sasuke, and Sarada.

They took Naruto to another dimension and bound him to begin the ritual of extracting Kurama from him, but the process proved to be too slow; Sasuke, Boruto, and the four other Kage arrived to rescue him. Kinshiki fought against the other Kage and was initially captured by them, but broke free from their techniques. He then unleashed a powerful blast around them, causing massive destruction and injured to himself. To everyone's horror, Momoshiki turned Kinshiki into a chakra pill and swallowed him to increase his strength, prompting Naruto and Sasuke to fight him and had Boruto use a Parent and Child Rasengan to finish him off for good.

Trivia

 * Similar to how Kaguya was named, Kinshiki's naming convention seems to follow the Japanese folklore motif. It is a reference to Kintarō, while Momoshiki is a reference to Momotarō.
 * Masashi Kishimoto's character sketch of Kinshiki shows him with normal-sized hands.