Hello,
First, let's set things straight. Indian companies threaten employees under the name of "blacklisting" them, so that they cannot get a job in the future. However, if you leave a company on short notice, absconding, or show insubordination, the employer CANNOT blacklist you from future employment.
If an employee discovers that a particular employer is hindering their future employment opportunities, they can sue the employer for a substantial sum of money in court and WIN!! The employer will have to face the consequences.
So, don't ever, ever think about blacklisting an employee. Things don't work that way. What you perceive as unfair may not be unfair to everyone. If an employee disappears or absconds from your organization, consider what you can do to reduce attrition rates, instead of resorting to unlawful shortcuts. That is the correct approach.
Please avoid getting involved in a class-action lawsuit. It would be highly detrimental to the company and your life, as the chairman will first hold you - the HR, accountable, along with the thousands of employees working under your supervision.