YOU SAID:
hello you are the stupidest person in the world
INTO JAPANESE
こんにちは、あなたは世界で最も愚かな人です
BACK INTO ENGLISH
Hello, you are the most stupid people in the world
INTO JAPANESE
こんにちは、あなたは世界で最も愚かな人々です
BACK INTO ENGLISH
Hello, you are the most stupid people in the world
That didn't even make that much sense in English.