I wouldn't worry about other damage he'll inflict... If a company has so little oversight that no second pair of eyes is reviewing his work, then it deserves to

I wouldn't worry about other damage he'll inflict... If a company has so little oversight that no second pair of eyes is reviewing his work, then it deserves to fail. Yes, as you have acknowledged, what happened is as much your fault as his. Bad apples do make their way into every organization, and oversight must exist. In any competent company that he gets a job next, he'll quickly be fired or reprimanded if he writes 12,000 line long methods. There doesn't need to be any further oversight than the standard industry oversights that already exist internally at companies.