Perfluoromethane

The emission of 1 kg of perfluoromethane (CF4) is equal to 7,390 kg of CO2 equivalents.

Tetrafluoromethane, also known as carbon tetrafluoride or R-14, is the simplest perfluorocarbon (CF4). Tetrafluoromethane is a potent greenhouse gas that contributes to the greenhouse effect. It is very stable, has an atmospheric lifetime of 50,000 years, and a high greenhouse warming potential 6,500 times that of CO2. Wikipedia