Cancer is a complex and varied disease, and it is difficult to say which type kills the fastest without taking individual cases into consideration. However, certain types of cancer are known to progress more rapidly than others. For example, Pancreatic cancer has a particularly poor survival rate, with most patients surviving only a few months after diagnosis. Other types such as mesothelioma, lung cancer, and brain cancer can be particularly aggressive and may also lead to a relatively short life expectancy. Ultimately, the speed at which cancer progresses depends on many factors, including the type of cancer, the stage at which it is diagnosed, and the patient's individual circumstances.