Yuuichirou Hanma

Yuuichirou Hanma, is the father of Yuujirou Hanma and grandfather of Jack Hanma and Baki Hanma. He is the only other person aside from Yuujirou to defeat the USA on a small island in the Okinawa territory during WW2. He is also known for defeating 2,000 US soldiers using one technique.

(Source: Baki Wiki)