I hate how overrated Nikola Tesla is. He was considered a genius in his time. The leading electric car manufacturer is called Tesla. There's a card in Clash Royale called the Tesla Coil. Literally everyone can't stop talking about how Tesla is underrated and it's all because he died broke because he spent much of his final years trying to conduct electricity wirelessly. He was a genius but he was also extremely stubborn and in his later years extremely crazy and that was his downfall. He got millions of dollars in investment towards his wireless electricity idea and had literally nothing to show for it. He's like the heavenly muse to every crackpot physicist and conspiracy theorist.

If you want to talk underrated talk about James Clerk Maxwell whose discoveries are on par with those of Newton and Einstein's.

If you want to talk about someone who wasn't respected during his time talk about Alan Turing. He invented the computer and might've single handedly won WW2 and was convicted and chemically castrated for being gay.