Interesting! Here's a name for you (although maybe you know): Gunnar Barlund! Do you have any other heritage links or just Finnish if you don't mind me asking (to add to your boxing list)?
Well I like Mauro Mina and he was quite the hero in Peru, but he is not an ATG and probably the best to come from there. But Mina deserved a shout out today anyway
Taking away the silliness of the term all-time, greatness really should mean something very special. So for Queensberry rules boxing, if you took the 35 fighters ranked by Rummy on his excellent thread: https://www.boxingforum24.com/threads/top-35-all-time-reveal-boxing-survey-series.653021/ You could argue only USA, UK, Philippines, Argentina, Brazil, Mexico and Nicaragua are in the argument for producing a great (Ireland, New Zealand and Canada having a * too)... So with them guidelines I would suggest Australia is the answer.
New Zealand, Mongolia, Vietnam, Northern Ireland, Ethiopia, Sierra Leone, Peru, Morocco, Luxembourg, Netherlands
Well by literal definition no one was calling him great in 1800.... Twenty three people here of sound judgement, between them did not have him in their best 35 fighters. If greatness is to be elite, I would suggest thus Griffo falls short and is merely brilliant. But I understand, this is abstract; others may have less strict criterion for greatness, and other sites may have different opinions on a top 35.