The NES dropped the hardwired controllers, instead featuring two custom 7-pin ports on the front of the console. Also in contrast to the Famicom, the controllers included with the NES were identical to each other—the second controller lacked the microphone that was present on the Famicom model and possessed the same START and SELECT buttons as the primary controller. Some NES localizations of games, such as The Legend of Zelda, which required the use of the Famicom microphone in order to kill certain enemies, suffered from the lack of hardware to do so.

Answer this question, if possible (if impossible, reply "unanswerable"): What did the Legend of Zelda require in certain instances to kill enemies?
Famicom microphone