League of Legends don't always run perfectly and the "A critical error has occurred and the process must be terminated" is an error that can boot players out of the game. Considering the error text doesn't have a reason attached to it, finding a fix may take a few tries.

LoL's critical error can appear when players try to launch the game. While you can run League without any problems on your second attempt, you may also need to apply some fixes to solve the problem in some instances. This League of Legends system error has been around for a couple of years now, so there are plenty of community-tested fixes you can check out.

How do you fix the critical error in LoL?

In my personal experience, I've mainly experienced the critical error in LoL after updates. It went away on its own after a short while, but there were a few times when I had to find solutions. The fixes below for the critical error were recommended by Riot Games' support team and here's how you can apply them.

Reset TCP/IP, Flush DNS, and Configure Port Forwarding

1. Open the Start Menu.
2. Search for Command Prompt (cmd) and run it as an administrator.
3. In the command window, enter the following commands one by one, pressing Enter after each:
• netsh int ip reset – Resets the TCP/IP stack.
• ipconfig /release – Clears the current IP configuration.
• ipconfig /renew – Requests a new IP address from the DHCP server.
• ipconfig /flushdns – Clears any outdated or corrupted DNS cache.
• netsh winsock reset – Resets Winsock settings to fix potential network socket issues.
4. Restart your computer for the changes to take effect.

Adjust Unicode Settings

1. Open the Control Panel.
2. Navigate to Change date, time, or number formats.
3. Switch to the Administrative tab.
4. Click Change system locale.
1. Set the Current system locale to English, OR
2. Enable Use Unicode UTF-8
5. Restart your PC to apply the changes.

Turn off programs with overlays

Background processes with overlays like recording programs, Discord, and similar can cause critical errors in LoL. If the problem persists after applying the methods above, you should close all such programs via the Task Manager.

Once all apps with overlays are closed, right-click the League of Legends.exe and navigate to the Compatibilities section in Properties. Select "Run this program as administrator" and "Disable fullscreen optimization" settings. Apply the changes and try relaunching LoL.

Considering this error often surfaces with new updates, Riot may also roll out hotfixes if the critical error affects a decent majority of the player base. For that reason, I'd also advise waiting for a few hours before contacting Riot support in cases where the error persists.