Hugh was a Borg drone rescued by the Enterprise-D who developed a sense of self and later worked to help freed Borg in the 24th century.
Hugh was a young Borg drone, known as Third of Five, found injured by the Enterprise-D in 2368. Picard planned to use him to spread a program that could destroy the Collective, but as Geordi La Forge cared for him, the drone began to develop a sense of self and accepted the name Hugh. Seeing him as a person, Picard chose not to use him as a weapon and returned him to the Borg.
Hugh's newly found individuality spread to others when he rejoined the Collective, cutting a group of drones off from it. Lost and confused, they fell under the control of Data's brother Lore, until the Enterprise crew helped Hugh free them. Decades later, in Star Trek: Picard, Hugh ran a project to help ex-Borg aboard a Romulan-held Borg cube. He was killed while helping Picard.
Hugh challenged the view of the Borg as a faceless enemy and showed that drones could become individuals again.