An investigation, and the legal system. Corporations exist because they make a deal with the state. In exchange for limited liability, they're required to respect the corporate form which entails things like meeting minutes, preservation of certain business records and communications, conducting audits, imposing oversight, etc. If they don't abide by these rules, plaintiffs can sue the company and bypass the limitation of liability to recover from individuals in their personal capacity.

This system of incentives and disincentives does work, and the US had a better handle on it in the past.