If one were to choose the most vastly underrated scientist of all time, Tesla would be a fine choice. Although Tesla was a true genius and a complete badass - contemporary society has largely forgotten the man that made modern technology possible.
Most people are at least vaguely familiar with Alternating Current (AC) - it is responsible for running most of our everyday appliances and electrical equipment. This was the work of Tesla. During the so-called ‘War of Currents’ of the late 1880s, while the renowned Thomas Edison was an advocate of Direct Current, Tesla spoke out against him - and was proven correct.
Besides all of this, Tesla also made enormous breakthroughs in the invention of fluorescent lighting. He also invented the super-awesome Tesla coil, shown below. Invented in 1891, version of the Tesla Coil are still used in radios, televisions sets and all sorts of different electric equipment.
Tesla even described the principles of wireless radio - causing one of the harshest science rivalries of all time. Guglielmo Marconi is largely credited with the invention of the radio, but Tesla expressed the idea years beforehand. Marconi used a number of Tesla’s 700 patents for creating the radio. Tesla eventually sued Marconi, and Marconi’s patents were declared invalid in 1935. In a feat of bad luck, Tesla died a few months before the law suit was finalized - and he was never given a penny of compensation