The Childe

A brief description of the manhwa Genius Grandson of the Loan Shark King:

During a family yacht cruise, “Jin Taeha,” the heir to Korea’s top company “Cheongu,” survived a terrorist strike by himself. He finds out that his family’s deaths were caused by power disputes among his relatives rather than an accident. As he enters the Italian mafia organization known as the “Salerno Family,” he gets ready to exact retribution.
He eventually starts his retaliation when he returns to Korea after 17 years.