game crashes on newer Windows when you alttab aswell so, don't change your resolution. do it though the ini file or the config tool.

how do use the config tool??? im using windows 10

Remember to run the game as an administrator, that prevents lofs of problems. You can also try out compability mode with Win 7 and older

Has anyone found a solution to this? Changing resolution doesn't work, the game doesn't start by running k2.exe in any way and the only configuration file I found was Documents\Kohan2\data\User\UVars.tgi, but it doesn't contain any resolution settings.

For anyone that struggles with this, I found the solution.
After starting the game at least once, look for the following file:
C:\Users\<USERNAME>\Documents\Kohan2\data\User\UVars.tgi

Open it in notepad and it under [Vars] section, add the following values to set the resolution:
int ResolutionX = 1920
int ResolutionY = 1080

If the file doesn't exist, create it and paste the following inside:
[Vars]
{
int ResolutionX = 1920
int ResolutionY = 1080
}

Change the resolution to whatever you want and the game will pick it up correctly.