Answer:
spendthrift
Explanation:
A spendthrift is a person who spends money in an irresponsible way, or in other words, wastes money.
The word "spendthrift" has a negative connotation because of the image of wastefulness attached to it.
The words "generous", "benevolent", and "philanthropic" are used to compliment people, and do not have any negative connotations.
