I suppose SectorC could win from the 'Assembly' entry.

[HenkPoley]

For various definitions of winning, probably disqualified because it doesn't run under an OS.

SectorC is a C compiler in a boot sector:

• https://xorvoid.com/sectorc.html
• https://github.com/xorvoid/sectorc

[MichalStrehovsky]

Yeah, this repo measures hello worlds. It would be ~20 bytes for a bootsector hello world, but I only measure x64 Windows.