One or more files in Opera's profile folder are probably corrupted. There are a lot of database files in there that can get corrupted if Opera isn't shut down properly. You should consider everything that you can't personally audit and verify in the profile to be damaged goods. You should rename Opera's profile and cache folders and start over. It's the only way to be sure things are 100% correct. The fact that you've had temporary profile problems before this crash is even more of a reason to start over.
With that said, take a look at https://help.opera.com/en/latest/crashes-and-issues/ to see what some of the profile files are for. After you start with a new Opera profile and cache folder, while Opera is closed, you could copy (not cut, so you still have the original old file) some files over to the new profile (overwriting the existing ones) to see if you can restore some things. There's just no guarantee that what you're copying isn't corrupted. You just assume that if you copy something over and it restores the things it's supposed to be storing, that it's not corrupted. But, you're always taking a chance.
For example, you could copy over your old History file. Then, start Opera and goto opera://history to see if your history is back. If not, then you know your history file was damaged for sure and you should delete the file again to start over with a fresh one. You could do the same with Bookmarks and BookmarksExtras.
You could try deleting the contents of the "sessions" folder and copying over the contents of the old sessions folder to try and restore your opened tabs. I would avoid this though as sessions get corrupted so easily from improper shutdown, the files are likely to be corrupted.
For your passwords, you can try copying over the "Login Data" and "Local State" files. Then, start Opera and verify your passwords are listed at the URL opera://settings/passwords.
For extensions, that's a little more complicated. First, you want to look in the "Extensions" folder in your older profile to see if the extensions are still there. Then, you can try copying them over to the new profile. But, you'll have to copy more then just the contents of the "Extensions" folder. You'll see other folders with "extension" in their names. You'll see the "Local Storage", "IndexDB", and "Databases" folders that you probably have to copy over too to retain each extension's settings. Further to actually retain the list of installed extensions and be able to use them, you'll probably need to copy over the Preferences file too. Maybe Secure Preferences and "Local State" too. Point being, the more of these thing you copy over, the more of a chance you're copying over something corrupted. That's even more so for the Preferences file. I haven't tested what's all needed to copy over everything for extensions. You'll have to experiment. But, I would avoid and just reinstall all your extensions so you know that are right.
Note that some files like the Bookmarks and BookmarksExtra files are JSON files. So, you could verify those with syntax checkers at least. Some othe files migh be SQLite database files that you might be able to check that they're not corrupted by using some tool. But, it's just easier to start over.
Also, because of the improper shutdown, you should check your system files. You should also check your filesystem. You should also check the status of your drive to make sure it's still good. I would also uninstall (don't tell it to delete your data when uninstalling) and reinstall Opera to make sure its program files are all good and not corrupted.
Once you have things all sorted out, it would be good to make frequent backups of the whole profile folder (and the cache folder if you really, really wanted to). There must be no Opera processes showing in the Windows Task Manager when you make a copy of the profile folder for a backup.
If you use Opera Sync, it'll be best to reset your data at sync.opera.com so that if you sign into sync in the new, good profile, you're not importing any old and possibly corrupt data. Also, avoid syncing settings unless you really need to. They can get corrupted by sync.
Further, you should export your passwords to a csv file as a backup too if you want. Goto the URL opera://settings/passwords, click the 3 dots to the right of "saved passwords", and choose export. That way, you can always import your passwords back in if you have to. You can do the same with your bookmarks via the drop-down on the opera://bookmarks page. You can save open tabs (for each workspace if you use workspaces) by right-clicking on a tab and choosing to save all in a speed dial folder. Then, when you back up your bookmarks, opened tabs will be backed up too. You can then import the bookmarks, right-click on the folder and choose "open all in tabs".
