JL Nehru: He committed some grave mistakes like:
1. Taking Kasmir issue to UN (1948) and stopping VB Patel invading Pakistan. This is the root cause of current Kashmir problem. India could not get its territories occupied by Pakistan in 1947-48.
2. Trusting china
(हिंदी चीनी भाई भाई), though this was the incident when India started to think about its very weak defense potential.
3. Mixed economy I mean
समाजवादी मिश्रित अर्थव्यवस्था
And I agree that Nehru was also partially involved in India's partition in 1947 as claimed in newly controversial book by (Former) leader Jaswant Singh. People also accuse him of power hunger.
LB Shastri: We respect Shastri Ji for his honesty, we read about him in our textbooks how poor he was, how he managed to go to school by swimming as he had no money for
"नाव", his mysterious death in "Tashkand" (whatever the spelling is) etc. etc. and we idolize him out of sympathy not for his achievements. And I do not see any big achievement by him as India's PM. His
historical
"ताशकंद समझौता" did not get India its parts Pakistan had occupied.
(Someone might accuse me for my ? superficial knowledge but thats what I have.)