Another one is the Flint water crisis. In Flint, Michigan, decisions were made to switch the water source to save money. But the water was not properly treated, and it became contaminated with lead. The local government initially downplayed the issue. This was a nefarious situation as it put the health of the entire community, especially children, at great risk due to lead poisoning.
The Bernie Madoff Ponzi scheme is a very nefarious real story. Madoff promised high returns to investors but was actually using new investors' money to pay off old ones. He managed to deceive many people, including charities and wealthy individuals. His actions were not only unethical but also illegal, and it took years to fully uncover the extent of the fraud.
Nefarious is purely fictional. It was made up by the writers and doesn't have roots in actual happenings. The story and characters are products of imagination and creativity.