At least in terms of the number of ant species described he is unchallenged:
With 1960 (still valid) ant species he described the most ant species of all myrmecologists.
At the age of 7, he began observing ants and at age of 25 he published his most famous work "The ants of Switzerland". Even Charles Darwin expressed his admiration in several letters. He was also a neuroanatomist, psychiatrist and eugenicist.
You can read more about him in his Wikipedia article.
Edited by Barristan, May 13 2021 - 2:07 PM.