https://prnt .sc/fm3962

It's a little technical to get it there, but it's an achievement from Spacewar and to get it you need to cheat the achievement.

First you need Steam Achievement Manager. I can't link it here because steam removes the link, so you'll need to google it. The website it's on is pink though, that's the official site.

Once you have it, run it.

In the "add appid" area up the top, type in 480 and add it.

Unlock all achievements if you want, all you need is "NEW_ACHIEVEMENT_NAME_0_4".

To add it to your profile, go to the achievement you want to change, right click on the game picker, and change the appid of any game to 480.

Select the game, and pick the achievement.

I hope I wrote this up right. Enjoy!

What about putting it in an achievement showcase?

Rarest achievement, not possible unless it actually is the rarest. Custom selection showcase however is already listed in my post above.

To add it to your profile, go to the achievement you want to change, right click on the game picker, and change the appid of any game to 480.

Select the game, and pick the achievement

Thanks