How to make Steam not count some games towards "Avg. Game Completion Rate"?

Solution 1:

According to user Lorean at Steam Community:

A quite late response, but I keep a spreadsheet to track my achievements and I just tested this. with some functions. Dividing completed achievements vs total achievements gives me 40%. Calculating the average of each individual game's achievement completion % gives a result of 52.11% which would match with my profile's average completion rate of 52%.

And furthermore, to answer your question. User Canti in the same thread:

Games that have no achievements are not factored in at all.

Likewise, games you have not earned any achievements in are also not counted. Only when you get 1 achievement will the game start to count it towards your average.

So games without any completed achievements do not count towards the Avg. Game Completion Rate.

More examples are given in the same thread. Here is user Boys Dont Cry:

I can confirm it's the average completion of all games played with achievements. Games with 0 ach. doesn't count But F2P and demo not any longer available like Call of Duty: Black Ops - Multier (I got 2 out of 3) is included in the total and the completion Rate

For games there I have at least 1 achievement: I have 1428 of max 2270 => 63% but average of percentage for each game => 68% same as on my profile page

Solution 2:

Unfortunately - no. There is no way to remove the "ghost" of achievements affecting your AGC ratio on Steam. Using some kind of unlock/relocker tool to wipe a game's achievements will actually only harm your AGC because if you have ever had 1 achievement in a game, it will forever affect your AGC and by taking yourself to 0%, you have only lowered it. Valve will not wipe/clear achievements for you if you contact them via support. Games where the DEVELOPER chooses to remove some or all achievements will properly update their affect on your AGC, however.

All of this confirmed via the complex stats on the https://completionist.me tracker and through extensive testing by the 100Pals official Steam achievement hunting community: https://www.discord.me/100Pals