The error message you're seeing suggests that there may be an issue with your graphics drivers or display settings. Here are a few things you can try to resolve the issue:
Update your graphics drivers: Make sure your graphics drivers are up-to-date. Visit the website of your graphics card manufacturer (such as Nvidia or AMD) to download and install the latest drivers for your specific card.
Check your display settings: Ensure that your display settings are configured correctly. Make sure that the resolution, refresh rate, and color depth are all set to values supported by your monitor.
Verify game files: Verify the integrity of the game files in the Pixelmon mod to make sure there are no corrupted or missing files causing the crash.
Allocate more memory: If the game is running out of memory, you may need to allocate more memory to it. To do this, edit the JVM arguments for the game by adding "-Xmx<amount of memory>M" (without the quotes) to the end of the "JVM Arguments" field in the game's launch options. For example, to allocate 4GB of memory, you would use "-Xmx4096M".
Reinstall the mod: If none of the above steps work, try reinstalling the Pixelmon mod from scratch to ensure that all files are installed correctly.
If none of these solutions work, you may want to reach out to the Pixelmon mod community or support team for further assistance.