How to tackle a vindictive boss in government service in India?

he is not what he appears to be. He expects you to open up with him in a group yet goes about spoiling your ACR from behind without any basis. He is powerful at the local level yet he too has several skeletons in his cupboard waiting to be exposed but for which you too might have to pay a heavy price, if you dare to. Since he had written baseless allegations in the previous ACR which will not stick in the absence of concrete evidence, he is now raising petty issues in order to inflate my service book in view of the next year's ACR. Pl. only people in govt. service in the know may answer this.