Henry Armstrong
Henry Armstrong was so good that it’s a legitimate coin flip between him and Sugar Ray Robinson for greatest of all time.
Armstrong is one of the few fighters in history to simultaneously hold world championships in three weight divisions. This is made even more impressive given that there were only eight recognized divisions at the time. Armstrong took on and defeated many of the notable fighters of this era. He won the World featherweight title from Petey Sarron in 1937 but quickly jumped up in weight.
He won the World Welterweight Championship in 1938 from Barney Ross and defended it a record 18 times before controversially dropping it to Fritzie Zivic in 1940. During his welterweight reign, he also captured the World Lightweight Championship, making him the featherweight, lightweight, and welterweight champion at the same time.