The game crashes instantly as soon as a world finishes loading or creating only with epic fight mod installed.
This is with the current latest version of the mod you posted 24 hours ago for 1.16.5.

Here is a detailed crash report:
crash-2021-11-22_13.23.39-client.txt

Caused by:
java.lang.LinkageError: loader constraint violation: loader (instance of sun/misc/Launcher$AppClassLoader) previously initiated loading for a different type with name "org/apache/logging/log4j/util/MessageSupplier"

To be honest, looking at the report, I have no idea what the source of the crashing is.
I hope you find a fix.

Found the fix and the problem!
The latest version of 1.16.5 forge does not work with the mod at all!
After I downgraded to the recommended version it worked perfectly fine!