Eh, a technical issue. It seems that this ultimate achievement cannot be unlocked, but the latest version (Version 1.2) has solved it. Thanks for the feedback from the players!
Fixed the bug where the ultimate achievement cannot be unlocked
Source: Steam Community (opens in a new tab)
Build and release context
Recorded Steam release date:
Within one calendar day of this post (UTC). The listed date does not establish an exact launch time.