Answer:
Daisy and Tom.
Step-by-step explanation:
Nick was referring to Daisy and Tom when he said, "They were careless people...they smashed up things and creatures and then retreated back into their money or their vast carelessness or whatever it was that kept them together, and let other people clean up the mess they had made." This statement reflects Nick's growing disillusionment with the wealthy elite of East Egg and his realization that they are morally bankrupt and indifferent to the harm they cause to others.