Greetings paxton4444,
Let's see if we can get that event permanently deleted.
Change General preferences in Calendar on Mac - Apple Support -- With the Calendar app open, select Calendar > Preferences > Accounts. Select the account and uncheck "Enable this account". Then close the Preference window and quit the Calendar app: Quit apps on Mac - Apple Support
Once your Mac is back to the Desktop, enable your account again in Calendar Preferences and delete the repeating event. If it still doesn’t stay deleted, please continue below.
How to use safe mode on your Mac - Apple Support -- If it reappears again, restart your Mac in safe mode and test the issue. Once you've had a chance, restart your Mac normally to exit safe mode. Please be aware that starting in safe mode may take longer than usual:
Safe mode prevents your Mac from loading certain software as it starts up, including login items, system extensions not required by macOS, and fonts not installed by macOS. It also does a basic check of your startup disk, similar to using First Aid in Disk Utility. And it deletes some system caches, including font caches and the kernel cache, which are automatically created again as needed.
If the issue didn't happen while your Mac was in safe mode, test the issue again after a normal restart.
Please let us know the results when you're able.
All the best.