As a Computer Scientist I feel a need to pitch one I couldn’t spot in the answers but deserves recognition: Alan Turing.

Let’s just quickly recap this guy’s achievements:

1. Father of theoretical computer science. This guy invented the Turing machine (could you have guessed?), a theoretical construct that he (alongside American mathematician and general badass Alonzo Church - Wikipedia) showed to exhibit universal computation. He straight up invented a theoretical model of a general purpose computer: if a function of natural numbers is possible, it can be done with a Turing machine.
2. Father of Artificial Intelligence (in its modern sense). The Church-Turing thesis meant that computers were capable of any logical deduction, making AI graspable. Only 2 years after his death, the field was founded formally. It’s worth noting that the field is commonly understood by outsiders according to the Turing test, another of his postulations.
3. Worked on cracking the Enigma code during World War 2 with GCCS. The team Turing worked with went on to crack German messages that were particularly useful in the Battle for the Atlantic. It’s hard to pin the success of the Allies in WW2 on any one particular factor, but upper suggestions for the impact that cracking the Enigma code have placed the number of lives saved by GCCSs actions in the realms of 14 million.

All in all, a hugely important man that changed history. Computers drive practically everything in the modern world, we increasingly see Artificial Intelligence as part of our future, and the sheer impact of Turing and others in WW2 for saving lives is amazing. So why was his life wasted? One simple reason, his sexuality.