AIO Installer that enhances most aspects of the game from character models to sounds, textures, weapons, UI and more with minimal conflicts just subscribe and 90% of the work is done
With just a few extra outside steps that are optional but will give the game a more cinematic look and feel

For full effect use Reshade: https://reshade.me
Using either this file for a bodycam look: https://www.nexusmods.com/readyornot/mods/1719
or my own files based on the above with a more cinematic look: https://drive.google.com/drive/folders/1HGUhaQAcoMwTMFb5AvxEe7iDNZ4SIjpf?usp=drive_link

How to install Reshade and Custom File: https://www.youtube.com/watch?v=e2qKbNzoMM0

Enable console in the options menu then press the tilde key ( `) to open console then

Disable Crosshair in console type: crosshair 0
if you need to renable: crosshair 1

Remastered 60fps VALVe Intro, Remove Survivor Names, Hide survivor id隐藏生还者id（Ai only）,Third Person Mode w/ Aiming Down Sights and the VOX - Complete Vocalizer needs extra steps read their addons for how to

Some addons only take effect in single player or in servers with these mods enabled but the majority of these mods work in public multiplayer lobbies

If you have audio and stuttering issues whilst it isn't foolproof for audio try setting a launch parameter for the game to do this right click on Left 4 Dead 2 in your game library and select properties when the pop-up window appears scroll down until you see launch parameters then copy and paste this command

-heapsize 750000

I've also found that for audio, updating and rebuilding the audio caches does sometimes help when you find audio cuts out on certain maps. You can do this when all addons are installed on the main menu in the extras tab first select UpdateAudioCache wait for the process to complete then select RebuildAudioCache

Bear in mind as well to make sure that your audio settings have your speaker configuration correctly setup as it has sometimes been known to cause issues

And if you have problems with stuttering going into the Left 4 Dead 2 folder directory can help. To get there go to your library and right-clicking on the Left 4 Dead 2 tab and choose manage> browse local files then when in file explorer go to left4dead2>cfg and find the file named "autoexec.cfg" you can turn this file into a text document, be sure to put a space if their is another command line above that may be in the file. Copy the command below and save the document

cl_forcepreload 1

Also in advanced video options try enabling or disabling multicore rendering may give a desired effect but i haven't found a difference with it so I leave it enabled

As well as this make sure that Paged Pool Memory Available is set to low otherwise your game might crash instantly when loading into a game

Looking on forums as well trying these might help

Unplug your mouse or keyboard and even Ethernet cable and plug them back in
Make sure you have a good internet connection
Try to Play on offline mod and turn off wifi and see if it does anything
Make sure the Harddisk L4D2 it's on installed isn't faulty
Reset every setting with these steps:

1-Go to your launch options (For left 4 dead 2)
2-Put " -autoconfig " command there
3-Start your game,then close it
4-Delete that command i gave you
5-Start and test it again

If that doesn't work try to turn-off Subtitles.

If that also doesn't work delete your custom CFG files

If that also doesn't work move Left 4 Dead 2 to a different HDD (if you have any) or reinstall it (Fresh install)

Make sure your drivers are updated.

If that also doesn't work disable in-game Steam Overlay for Left 4 Dead 2

If your on Windows 11 exclude the Left 4 Dead 2 game folder in virus and threat protection so that the files aren't being scanned whilst in-game

Link to my in-game settings-
https://drive.google.com/drive/folders/1CDmowFUs6BUfqLngXfXaYF85T9AG4HHr?usp=drive_link

This should in some cases help alleviate problems but as i've said before this may not fix all if any issues you are having they're just extra steps that might help