Much of the data that we need are corrupted.
Much is singular,therefore the sentence should be "is corrupted"
You could use many of the data/are corrupted
Data is plural, hence I think are is used correctly.
Rupam, you cannot be suggesting that 'much' is plural, can you? If you are, you are wrong.
Will is right. Rupam is wrong.
The issue here is with ''Much''
I think it should be ''Most''... and also ''data are'' is quite awkward
''Most of the data we need is corrupted'' sound simpler!