IMHO, the most truly remarkable thing about Einstein was the diverse range of subtopics in physics he contributed essential knowledge to. His 1905 paper included:
-a study of Brownian motion (the first self-contained empirical method of measuring molecular/atomic masses)
-the photoelectric effect (essentially the discovery of photons, which is actually the theory that won him the Nobel Prize)
- AND special relativity.
Later in life he contributed general relativity, important theories in quantum statistics and the specific heats of solids, and to the development of quantum mechanics and cosmology.
Any one of this vast number of contributions would have been enough for most physicists to say they had a successful career.
Also heat capacity.