MySQL may not start if its data files are corrupted.

If MySQL was not shut down properly, it may cause issues on restart.

1) rename xampp\mysql\data => xampp\mysql\data_old

2) create new folder xampp\mysql\data

3) copy everything from xampp\mysql\backup to xampp\mysql\data without ibdata1

4) copy all YOUR (skip mysql) database folders from xampp\mysql\data_old to xampp\mysql\data

5) copy file xampp\mysql\data_old\ibdata1 to xampp\mysql\data\

6) start mysql

Reference : https://www.youtube.com/watch?v=6iLue3EFBWU&t=18s