'It is sad to see a man so corrupted by the desire for money and power.'
'see' is mean that by using speaker's eyes? o_O
Here, see might mean to be using the eyes to see.
But, more probably, here it means to just knowing or noticing someone who is corrupted.
It could have two meanings in this sentence -
"It is sad to see a man [who is/has been] so corrupted by desire for money and power."
In this sense it describes that it is upsetting to see that it is possible for him to be so corrupted, or that it is unpleasant to see the state that he is in and how he acts as a result.
Or it could be "It is sad to [have witnessed] a man [become] so corrupted by desire for money and power." Here the verb 'see' is used more to indicated having seen or watched events occurring.