I am considered a great in my field.
If you remove the first three letters of my surname, the remaining letters are twice of what you get when you remove the first three letters of my forename. What's more, the letters that remained in my forename also appear together in the name of my birth country.
Who am I?
I think you're looking for:
Swiss tennis legend, ROGER FEDERER.
If you remove the first three letters of my surname, the remaining letters are twice of what you get when you remove the first three letters of my forename.
Remove the first three letters of first name and surname and you have:
(-rog)ER (-fed)ERER
i.e. ER and ERER
where the second is clearly twice the first!
The letters that remained in my forename also appear together in the name of my birth country.
Federer was born in SwitzERland, which also contains this two-letter substring.
You are
Kim Chŏng-ŭn, AKA Gim Jeong-eun, AKA 김정은, usually AKA in English Kim Jong-un, i.e. the Supreme Leader of North Korea
I am considered a great in my field.
Especially in North Korea, you are a great politician, an undisputed natural leader that is second only to your grandfather.
If you remove the first three letters of my surname,
If you remove three letters from 김 (Kim), you get an empty string (note that 김 is three letters both in the original (jamo) and the transliteration(s))
the remaining letters are twice of what you get when you remove the first three letters of my forename.
The remaining letters form an empty set, which is twice of an empty set that you get when you remove three letters from Kim (because in Korean, surname comes first and is therefore a forename as well). You can also argue that removing three letters from 정 (Chŏng, which is three letters long in the original) gives you also an empty set (neglecting the 은), if you disagree with this definition of a forename.
What's more, the letters that remained in my forename also appear together in the name of my birth country.
trivially, an empty set is a subset of any set
I think it is
Linus Pauling, born in United States
I am considered a great in my field.
He is one of the greatest chemists. He published in 1939 "The Nature of the Chemical Bond", which is a major pillar in chemistry nowadays.
If you remove the first three letters of my surname, the remaining letters are twice of what you get when you remove the first three letters of my forename.
Removing the first three letters from Pauling would give us LING which has 4 letters. Removing also the first three letters from Linus would give us US, which has 2 letters, that is exactly half of the surname letters.
What's more, the letters that remained in my forename also appear together in the name of my birth country.
Well, if removing the first three letters from Linus give US as a result it is perfectly linkable to United States (US)
Alternate answer, based on the OP's comment:
you are
John Flynn (though we do not know which one)
I am considered a great in my field.
Yes. You have a Wikipedia page, after all.
If you remove the first three letters of my surname, the remaining letters
[Fly]nn
are twice of what you get when you remove the first three letters of my forename.
[Joh]n
What's more, the letters that remained in my forename also appear together in the name of my birth country.
n appears in the United States and United Kingdom (or Britain or England...) and even in the Commonwealth of Australia
