What are the faultlines which hindered the consolidation of India is still not complete, particularly in the north east, even after 70 years of independence?

What are the faultlines which hindered the consolidation of India is still not complete, particularly in the north east, even after 70 years of independence? (GS 1)

भारत की समेकन में बाधा डालने वाली वो कौन सी फॉल्टलाइन हैं जो अभी भी पूर्ण नहीं हैं, खासकर उत्तर पूर्व में, 70 साल की आजादी के बाद भी?