In Windows Explorer (File Explorer), with "File extensions" and "hidden items" enabled under "View -> Show", in both "C:\Users\yourusername\AppData\Roaming\Opera Software" and "C:\Users\yourusername\AppData\Local\Opera Software", rename "Opera Stable" to "Opera Stable old" to start with fresh settings and data. Then, try starting Opera.

If Opera starts fine, then you know the issue was in one of the folders. If you're happy, you can just start using Opera again.

If you want to try and fix things, close Opera and delete the new "Opera Stable" folders that Opera created. The, copy the "Opera Stable old" folders and paste them to create copies. Then, rename those copies to "Opera Stable". Then, try starting Opera to confirm that it still crashes. If so, first try deleting the "Sessions" folder in "C:\Users\yourusername\AppData\Roaming\Opera Software\Opera Stable\Default" to see if that fixes it.