What to do if an employee has breached the contract of the company

I have breached a contract with some private company I was working with due to some personal issues and non-transparency with that previous employer and joined another company. The previous employer made me sign a bond of 50000/- and kept some mark sheet into his custody which he was supposed to give me back after. smooth exit. The reason I left my previous co. was that They were deceiving me. I was paid under wage and my P.F. was not deducted by them after several reminders for first 3 initial months. when I raised the issue they started deducting my P.F. Even they are not handing over my medical insurance Card even after deducting some amount from lst six months. He force the employees to work on saturdays too knowing that the market is off on saturdays. He don't even pay us for sundays. He is suppressing his employees to work on his terms and conditions that is an exploitation of employees. No sick leave,No casual leave are given. So, I left. now he is threatening me of lawsuit.