Kindly be more specific as the title is misleading,
if you mean your friend has used credit to tune of 5lakhs and is unable to make payments which brought down his cibil.
here's what can be done..
1)What exactly brought the amount to 5 lakhs Incase if it were products either refund or sell.
2)Ensure more than min payment is done always .
3)In the event he is unable to clear even min amount, reach out to bank to have pending amount as emi and make sure it's paid promptly