I think the pinnacle goes to MS-DOS 7.1, which while bundled with Windows was also usable as a DOS by itself and contained features like FAT32 support. MS-DOS 8

I think the pinnacle goes to MS-DOS 7.1, which while bundled with Windows was also usable as a DOS by itself and contained features like FAT32 support. MS-DOS 8 was the last version that came with the ill-fated Windows Me and significantly neutered.