Statistical boxing website BoxRec rates Thil as the second-best European boxer ever across all weight divisions, after Joe Calzaghe.

Thil was a journeyman boxer for a number of years but as he gained experience and matured to his optimal power, he developed strength in both hands and began to win regularly by knockout (KO).

[3][4] In addition to defending the IBU middleweight championship, Thil moved up a weight class to win the European light-heavyweight title in 1934.

After successfully defending the IBU and Ring Magazine middleweight titles 11 times, Thil fought Fred Apostoli in a non-title bout on September 23, 1937, in New York City.

It was a non-title affair because the New York State Athletic Commission, which recognized Freddie Steele as the world middleweight champion, said they would sanction the fight only if Thil agreed not to put his championship on the line.