Deleting it will break any application that depends on it. Only remove it if you are certain no program on your system uses Lua 5.3.3.
: The "r" likely stands for "Release" (as opposed to "f" for "Final" or "d" for "Debug"), indicating a specific build of the Lua 5.3.3 library used by certain game versions or DLC dependencies. The Common "Missing DLL" Issue Users frequently encounter an error stating lua5.3.3r.dll
Some anti-cheat systems use Lua scripts to monitor player behavior. A missing lua5.3.3r.dll could prevent these security modules from loading. Deleting it will break any application that depends on it