During the second fight against Piston Honda you can win the bout by scoring only one punch. Dodge his punches but don't retaliate. Then when he goes into his Piston Punch routine, hit him in the stomach like in the first fight. As in the first bout, if you time it right he'll be down. Unlike the first fight however, he will be too unsteady to keep his feet. I've even seen him be unable to get up. Keep in mind that the charging time for his Piston Punch routine is a lot shorter so you really have to time it just right or you'll just end up taking major damage.