Give an example of a situation in which an individual's pursuit of economic self-interest may not benefit but instead harm the rest of society

The correct answer is: "The Tragedy of the Commons".

The Tragedy of the Commons refers to the depletion of public goods and resources, to which all individuals have equal and open access, when each individual uses or consumes them attending to his personal interest and disregarding the survival of the resource. Such behaviour goes against the welfare of the totality of users, and even against the long-run interest of the individual, as if the resources is extinguished he will not be able to use it in the future either.

For example, fishing-stocks are overexploited, because each fisher captures a larger amount than they should if they wished to maintain their rate of reproduction and, as a result,  in same years there will be no fish at all. But, instead, fishers are moved by their individual interests, by the desire of maximizing the profits gained by selling the fish, and in order to do so they capture everyday as much fish as they can. They would never set an upper bound to their captures, thinking about the higher purpouse of preserving the fishing-stock.

a factory opens that mass-produces light bulbs.

explanation:

not sure if that's an answer to your questions but this is an example! : )