Hello!
I was having the same problem that a lot of people were posting about, with Safari crashing within seconds of opening it after the latest update. I spent a while talking to tech support, and this is what they told me to do (keeping in mind that I already tried fixing it in Safe Mode, tried opening it from the Applications folder, tried restarting my Macbook, and was able to access Safari in the guest account).
I was told to try and do a Disk repair ( which didn't work for me), and was told to try and Reinstall the OS if the Disk repair didn't work.
To do this, you go to restart your Mac, and as its restarting hold down Command+R keys until a utilities screen appears. Then select "Reinstall macOS", click continue, and follow the instructions on the screen. When it asks what disk to use, select your current OS disk (this was the only one that showed up for me). It took around an hour for the OS to reinstall, but now it's working perfectly fine!
I hope this helps (and thanks to the nice tech support lady who taught me how to do this)!
