I found myself unable to login after downloading the new expansion Witch Queen for Destiny 2. I tried everything; restarting my computer, verifying the integrity of the game files, running CC Cleaner, uninstalling and reinstalling, nothing seemed to work.
For those of you having an issue with the game crashing immediately when logging in, this fix worked for me. Disable mouse/keyboard software, in my case it was the Razer Synapse. You can also disable Razer GeForce experience. Anything that is running in the background, open up your task bar, right click and quit most things (obviously nothing imperative for your system to run).
Load up Destiny 2 after closing mouse software, keyboard software, Nvidia geForce ETC and it should be working just fine. This worked for me, and I was able to reopen all my peripheral software after the game loaded up.
Hope this helps! See ya in the Throne World