Too many breakthroughs in the fields of general physics and quantum / theoretical physics to list. Equal in merit.... mostly due to the fact that they are owing to one another. Or, at least, rely on them somewhat.
If I had to pick one thing. It would be the development of the lens. Helping billions to see, lazer technology, data storage, photography, filmography, projection etc etc etc. From Galileo Galilei to cosplay eyes. It all adds up.
I realize electricity has, probably, done more for us as a species.... but to be fair it already existed we simply harnessed it. In the same vein. Nature gave us the lens. I just feel that we have redesigned and applied the lens, more so. Making it, seemingly, more our achievement.