A key figure is a person or thing that plays an important role in something, and their actions have significant impact. It can refer to someone who holds a high position of power or responsibility within an organization, whose decisions and leadership greatly influence its success. In other contexts, it may describe a crucial element or aspect necessary for the proper functioning of something, without which the whole thing would fall apart. Essentially, being a key figure means having significant importance in shaping events or outcomes, whether positively or negatively.