What is the fastest you have seen someone progressed at chess ?

[Chessqueen]

Bobby Fischer went from 1726 to 2231 in less than a year, gaining over 500 points from the USCF's tenth national rating list published in May 20, 1956 to its eleventh national rating list published in May 5 of the next year. That was the span during which he played his Game of the Century against IM Donald Byrne. It's particularly impressive given that Fischer did it in the pre-engine, pre-ratings inflation era. Two months later he'd break into the top ten American players, and a month after that he'd win the US Open, the youngest ever. Fischer didn't stop rising — by March of the year after he was at 2626, exactly 900 points higher than not even two years prior, second in the US behind only Samuel Reshevsky. He had just turned fifteen years old.

The youngest GM ever gained over 130 Elo from March to June of this year, which is close to 500 Elo in a period of 12 months compared to Fisher
https://ratings.fide.com/profile/30920019/chart