I'm near my wits end. I've had this game a while now, and have put a lot of hours in. In the past I've had the same Corrupt Update Files (or Corrupt Download Files) error from Steam, but just for Conan. I've even uninstalled, restarted, and attempted to reinstall on a completely different HDD just to try to negate this error. It won't even complete the download/installation to a point where I can actually verify the files in it. I can't play at all now and I just (foolishly?) purchased the season pass earlier this month.
I've tried almost everything. Ran Chkdsk before the attempted reinstall. endless verify files attempts, steam is running as admin, tried setting all the files to Not read-only, nothing else was running but steam. Cleared download cache. Manually cleared the cache. Changed download region.