After doing a little research I just discovered something interesting. We've never had a fighter in men's boxing hold
World & Olympic titles as an amateur and then go on to become
undisputed as a professional. Usyk is the only guy to ever do it. The World Championships were inaugurated in 1974 so this achievement spans the last 50 years of boxing. That's a half-century. Some of the other greats, like Pernell Whitaker, came close but he had to settle for silver at the Worlds. Lomachenko was also very close recently. He would've done it had the Haney decision gone his way.
As an amateur World & Olympic champion, Fighter of the Year (2018), World Boxing Super Series tournament winner (Ali Trophy recipient), and a two-division undisputed champion in the pros, Usyk is one of the most decorated boxers of all-time. There's nothing left for him to win except perhaps Fighter of the Decade. He's reached the pinnacle of both versions of the sport despite turning pro so late.
The full list of undisputed champs is below. It covers the two, three & four-belt eras. I've already verified this but you can independently check their senior level amateur credentials. As you'd expect some of the other undisputed champs dating back to 1974 have won either an Olympic or World title as an amateur—but not both.
List of undisputed world boxing champions
