Name: Sesshomaru
Age: 200+
Species: Daiyōkai
Affiliation: Inu yōkai
Occupation: N/A
Weapons: Bakusaiga (Currently), Poison (Currently), Claws (Currently), Tokijin, Tenseiga
Abilities: Flight, Superhuman Olfactory Senses, Acid Claws, Acid Whip, Poison Body, Superhuman Strength, Superhuman Agility, Poison Secretion, Divine Powers, Electricity Control, Feral Mode (Inu Yokai Form), Fire Control, Healing, Immortal, Superhuman Intellect, Invulnerability, Magic Abilities, Necromancy, Shape Shifting, Size Manipulation, Superhuman Stealth, Superhuman Stamina, Telekinesis, Telepathy, Teleportation, Superhuman Tracking, Master Swordsman, Weapons Master, Unarmed Combat Master
vs.
Name: Byakuya Kuchiki
Age: 200+
Species: Soul
Affiliation: Gotei 13, Soul Society, Kuchiki Clan
Occupation: Shinigami Captain
Weapons: Senbonzakura, Senbonzakura Kageyoshi
Abilities: Superhuman Agility, Death Touch, Divine Powers, Energy Absorption, Energy Manipulation, Energy Shield, Force Field, Superhuman Intellect, Levitation, Kido, Superhuman Stamina, Superhuman Speed, Master Swordsman, Teleportation, Weapons Master
Scenario: Both are able to use any abilities they possess. Sesshomaru can use Bakusaiga and his Inu Yokai form. Byakuya can use both his Shikai and Bankai, Kido is also allowed. Pretty much no restrictions. Neither one knows of the others abilities. Any limitations in the show or manga are prevalent in this battle
Restrictions: Sesshomaru is not invulnerable / immortal.
Location: Feudal Japan, they start 20m from each other and have a super calm but badass conversation before going at it.