This Guide will reset everything back to playable.
Six easy steps that work perfectly to restore the game.
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The Guide will require you to find and manipulate the AppData folder in Windows.
The AppData folder is a hidden folder within your user profile where Windows stores application-specific data, settings, and files.

To unhide the AppData folder in Windows;
1 - Open File Explorer from the taskbar;
2 - Select View. Go to Options and select Change folder and search options.
3 - Select the View tab. In Advanced settings, select Show hidden files, folders, and drives.
4 - Select OK. All hidden files and folders are now visible.

Most players will then find the CS2 AppData folder here;
C:\Users\(your Windows user name)\AppData\LocalLow\Colossal Order\Cities Skylines II
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PREAMBLE >>>>>, before you do anything make sure you purge your root drive of any CS2 save files copies or directories that you may have created in the past. Be sure there are NO OTHER STEAM PROFILES on your computer that may have left any CS2 saves anywhere on the root drive as CS2 saves left in another profile if corrupt will halt loading all profiles as the game verifies every save on the root drive.<<<<<<

STEP 1 - Second to mods the biggest source of crashes and errors is CORUPT SAVE FILES.
Navigate the AppData folder to the "\Cities Skylines II" folder
Now, MOVE (not copy) the entire "Saves" folder to a drive other than "C"
This instruction requires you to "Move" the entire save folder OFF of the C "drive".

Some crashes and mod irregularities can be caused by corrupt Autosave files.
It may be good to delete all the old Auto Save files before moving the folder.
If you had a corrupt save this alone might correct an error but will happen again if you put the corrupt save back.

Alternatively you can just delete the "Saves" folder completely if you don't care about past saves.
If you want to preserve old saves do not simply copy them elsewhere, windows may still find them if left in the boot path.

If the suggestions in the above Preamble did not work then please follow the next 5 steps exactly;
If the game did not load after dealing with the saves your problem is likely caused by mod or PDX custom map or asset pack corruption. Continue with the steps below.

The following will fix the error or crash. This simply resets your game settings and will do no harm.
Please follow every step in order and do not modify or omit any. Each step is designed to correct specific known errors, miss one and if it still crashes start over and do the whole procedure in order again. Please do not ignore any step as that one missed step may be the item needed to correct your error.

STEP 2 - Login to PDX Mods and temporarily disable all mods and playsets (if any)
https://mods.paradoxplaza.com/games/cities_skylines_2?orderBy=desc&sortBy=best&time=month

STEP 3 - Ensure Steam Cloud Sync is "Off"
https://steamproxy.com/steamhelp/en/faqs/view/68D2-35AB-09A9-7678

STEP 4 - Now, back to AppData and delete ALL the other folders and files left within the "\Cities Skylines II" folder.
DO NOT delete any other folders or files from any other game folders in AppData.

STEP 5 - Now do this "Steam verify files" thing and restart With "Code Mods Disabled"
https://steamproxy.com/steamhelp/en/faqs/view/0C48-FCBD-DA71-93EB

STEP 6 - Important! Start a new map and do a New Save and then restart again with Code Mods Disabled before restoring your saves folder back to where it was. When the game is back up carefully restore your mods and assets.

The above will get you back and running for sure if you have any old mod, save or custom map or asset causing the failures.

However, it may come back again in future as you enable mods or custom maps and assets, just do it again if you need. It is easy and no harm to anything.

Thank you to all who contributed to development and tested this ongoing community effort.

Good luck! Enjoy!
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