Albert Einstein (1879-1955) is considered to be one of the most influential physicists of the XX century. He developed the general theory of relativity, where the formula E=mc2 was born. He is mostly known for this theory and formula. In 1921 he was awarded the Nobel Prize for physics for his explanation of the photoelectric effect. Moreover, his work on atomic energy was also important.
Einstein was German and Jewish, so when Germany became Nazi, he had to flee to the U.S. becoming a refugee. He had always been a pacifist, however, one of his biggest mistakes led to the creation of the atomic bomb since his formula E=mc2 helped to discover it. Also, he always regretted having encouraged President Roosevelt to finance nuclear research, even though that helped the U.S. to be ahead of Germany. In any case, he said that “a person who never made a mistake, never tried anything new”.