Speaking to reporters outside the court he said he regreted that he "failed to control impulsive emotion" and apologised for causing trouble.
The dramatic details of the case, which media have likened to a gangster movie, has drawn intense public interest in South Korea, where the heads of family controlled conglomerates wield great economic, political and social clout.
Victims have told police the elder Kim and his bodyguards took them to a mountainous area south of Seoul, where Kim himself allegedly assaulted them, including hitting one of them on the back with the large steel pipe.
Hanwha was established in 1952 as the Korea Explosives Corp before later developing interests in petrochemicals, finance, insurance, construction and retail.
Kim, South Korea's ninth-richest man, is said to be worth about $920m.
It was not immediately clear when the court would rule on the case.