This page describes Bare-Fist Battle Style in each of the games in which it appeared.
Soul Blade[]
When the character's weapon breaks, they use their bare hands for the rest of the fight. This was discontinued in later games.
Soulcalibur II[]
The PS2 Guest Character exclusive, Heihachi Mishima uses Bare-Fist. However, he has armguards to compensate a lack of a weapon (However, he uses his bare fists as his ultimate weapon)
Soulcalibur V[]
The Devil Jin fighting style is the second weaponless fighting style since Soulcalibur II with Heihachi. The fighting style is based on his Tekken 6 moveset where he can perform very powerful but yet difficult devastating combos that leads to very punishing damage that rivals Nightmare in terms of sheer force against the opponent. Prior of using the "Tempered Fists" the style also allows the player to perform laser beams from the eyes and flight movement simliar to Kratos and Aeon. Overall the range is quite short and the style is only available for only customs characters. It is banned from tournaments.
SoulCalibur II PS2 Heihachi's Command List
Soul Calibur V 'Soul of Devil Jin Move Set'