“The worst compression ratio recorded is for Disco Elysium: The Final Cut (9.5 GB –> 7.8 GB, only 17.9% saved), while the best result recorded is for Boomerang X (10.8 GB –> 859 MB), with a whopping amount of 92% traffic saved,” FitGirl reports.

FitGirl is probably one of the best known people in the world of pirated video games. She's a "repacker": she doesn't break the protection of the games, she takes games already unprotected by warez groups and recompresses them so that they are more compact.
And it does a pretty impressive job. For example, the entire collection of "Portal" games is normally 47.1 GB. She has reduced that to 7.8 GB. ‒ translated from the french comment of sebsauvage

(original source: https://fitgirl-repacks.site/amelie-report-october-2021/)