As of my knowledge cutoff in September 2021, the largest criminal fine in history was imposed on the pharmaceutical company Pfizer. In 2009, Pfizer agreed to pay a $2.3 billion settlement for illegally promoting certain prescription drugs for unapproved uses. This case involved multiple violations, including marketing drugs for uses that were not approved by the U.S. Food and Drug Administration (FDA) and providing kickbacks to healthcare professionals. The fine was a result of a legal settlement to resolve criminal and civil allegations against the company. It is worth noting that this information may have changed since my last update, so it's advisable to verify the latest data.