Thanks to lylat for sharing this info on AStats, and f*** you, AStats, for throwing away so many valuable resources from the achievement hunting community.

1) Forward these ports of your router:

Game: 7777 to 7778
Query: 27015 to 27016
Protocol: TCP and UDP

You should have something like this:



If you don't know how to portforward your router, check the next section of this guide.

2) Follow this post to learn how to host your server. Make sure to set an admin password to grant yourself access to the remote console. I recommend the EP-OmaniArena map, and setting a password doesn't really matter since the game is absolutely desolate.

⠀⠀⠀⠀⠀⠀⠀   

3) Launch your game, click on multiplayer and join your server.
4) Press F8 or F9 (recommended) to open the console, and throw this command (don't use the⠀ "<>", it's just syntax):

adminlogin <password>

5) Use this command to speed up the game:

adminsetgamespeed 2

6) Score a goal and throw this command to finish the match:

adminsettime 1

7) During the wait time between matches, throw this command to skip it:

adminforcerestartnow

8) Repeat the steps 5), 6) and 7) until you get the achievement. You can use this AutoHotkey script to make the process a bit more convenient:


Right click: Ends the match.
F2: Close the script.
F3: Skip the wait time.
F4: Speed up the game.

Forward the ports of your router is like setting up the BIOS of your PC, varies depending of the model of your router. There are two ways to portforward your router. The automatic way using the Network Utilities software from portforward·com, which is a paid app (you can't portforward with the free trial I think). And the manually way, which I'll cover right now.

1) Open your web browser and in the search bar, type your default gateway. The default gateway is usually 192.168.0.1 or 192.168.1.1, but you can check it anyways by pressing Windows + R, typing cmd and throwing the following command:

ipconfig

2) You will get and advise saying the connection is not secure, just dismiss it by clicking on the Advanced button > Continue to 192.168.0.1 (unsafe).



3) Now you will see a login page asking you for a username and a password. The username and the password are usually "admin" (without quotation marks). The password can also be the model of your router. This data is usually displayed in a sticker which is in some part of your router. You can also call to your Internet provider to ask for this info. You can also ask for the model of your router. This will help you to search for tutorials later in case you need it. Is usually displayed somewhere after you login, but no hammer on asking to save yourself a bit of time looking for it.

3) Now you must look for the portforwarding section. In my case is under the Advanced section.
4) Add a new IPv4 rule. You will need the following data:

• Local/Internal IP/Host: This is your IPv4. You can check it using the ipconfig command.
  
• Local/Internal start and end ports: You can check the default ports which a game uses making a quick search in the Internet. Here is a list where there are a lot of games with their default ports and protocols. You can also change the default port to make your game use another one.
  
• External IP/Host: Doesn't really matter. You can leave the default value, a 0.0.0.0, an asterisk (*), an empty field, depends on the model of your router.
  
• External start and end ports: They are usually the same as the Local/Internal start and end ports.
  
• Protocol: Search for it like the Local/Internal start and end ports.
  
• Setting a description or a custom service name is a good practice to remember in a future what thing is using or used to use those ports.

5) If you don't have plans of using the ports you forwarded anymore, make sure to delete the rule. Here are some tutorials in the case you can't find the settings:

https://youtu.be/X4LE7UFCtEE
https://youtu.be/LtkOeZ907p0
https://youtu.be/wJsNH51dkBs