Hey! Have you played every mode 10 times? That should trigger it.

There are more tips for achievements here: https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=211896413

Originally posted by Mirakos:

I've got all the entries in my library, but the achievement didn't unlock.

After collecting all the others I'm unsure what to do now.

Any ideas?

I have the game since 2012 and until now i was trying to figure it out how to unlock this last achievement, the dev there said to play 10 times each mode in the game... Well to unlock this i did the follow:

Peacefull Mode: 10 times
Hell Mode: 10 times
Remix: 2 times (and unlocked of nowhere)
Just remember that you need to do this in the same session if you leave or need to close the game, too bad because you're going to need to start it again... I dunno if that's the correct way to unlock it, but i did following these steps...

I have filled every library entry and played each mode 10 times and it still has not unlocked!

I have the same problem.
I already played all the modes 10 times (even Peacefull (?)).
I have my library at 100% and my developer's library at 63%.
I did what *OCB* Pekusuii | Shu did, but to no avail, in my game that achievement is the only one left.
Or do you need to fill all the Developer's library too?