• Again, this guide is focused only on Android. And better rooted.
  
• You might need to get root. If a directory is inaccessible or something else happens — get root. Try kingroot, but it is the worst option.
  
• Preferrable file manager is Total Commander, but if you're ok with how Linux (and Android) stores files, then you can proceed.

On your phone, navigate to directory

See all these files, starting with "Steamguard-"? After the dash goes that account's Steam ID, that is used in profile links.


HERE, CAREFULLY!!! BEFORE DOING SOMETHING, GO BACK, COPY THE FOLDER AND PASTE IT SOMEWHERE. Always do backups. If you accidentally delete your main account file here, you will have to recover your Steam 2FA, which will lead to a temporary trade ban on that account.

Only then continue with finding the one you want to delete, then open recent apps, close steam (no need to do brute stop, just close), launch it again and check if it worked. If it didn't, restart your device to be completely sure that it's all your fault. If it persists after the restart, read the next section.

Lost? Frightened? Confused? GOOD!

As I previously said, these numbers after that dash are Steam IDs.

Here you have two ways:
1) If you can access that account that you want to delete, do it. After that open your profile.

• If the link starts with https://steamproxy.net/profiles/, just copy the numbers.
  
• If there is /id/ instead of /profiles/, copy the link, go to SteamRep[steamrep.com], paste it there and press Search. There, under your name, there's going to be your Steam ID. ...that you could get by just going to your profile if only you had no custom link specified.

Now remember some of the last characters of that ID, take your phone in hands and delete the file that has that ID. All done.

2) If you don't remember anything, or don't even know what the hell is going on, just copy all these IDs one by one into the end of this link:

Find the ones you want to keep in your app and then delete everything else.