Are you having an registered agreement for sale executed and registered between you and first party??
if so than issue a legal notice to seller to promptly remove car from black list as you have legal purchased it from him and if any claim from third party pending the first party has to settle it its not your liability. On failure to act in accordance of notice the first party shall be liable to pay damages and criminal complaint for same can be filed.
Secondly make an covering letter attach the agreement copy and send to rto with request to transfer and for record, also furnish prescribed forms signed by seller for transfer. Further make a request rto to remove name from blacklist as first party has illegally done so. RTO will look into the matter.
Also what is the case pending on the vehicle???.