How can I solve - Error: MySQL shutdown unexpectedly?

Instead, you can first try using the MySQL backup folder which is included with XAMPP.

So do the next steps:

1. Rename folder mysql/data to mysql/data_old
2. Make a copy of mysql/backup folder and name it as mysql/data
3. Copy all your database folders from mysql/data_old into mysql/data (except mysql, performance_schema, and phpmyadmin folders)
4. Copy mysql/data_old/ibdata1 file into mysql/data folder
5. Start MySQL from XAMPP control panel.

This is a temporary solution, not a permanent one. We strongly recommend backing up your data and reinstalling XAMPP after restoring it. This error is caused by a malfunction of some files in XAMPP, not the database.

Important: Please don't delete the ibdata1 file. You could destroy all your databases.