2. Seven of Nine
Arguably the defining character / subject of the Star Trek: Voyager series, Jeri Ryan's orphaned Borg drone was the designated representative in the Federation/Borg alliance against Species 8472. After neutralizing the Species 8472 threat, Seven of Nine attempted to assimilate Voyager's crew and was then separated from her collective. In the seasons that followed, Seven of Nine would be slowly integrated into the Voyager crew, with the majority of the crew resisting trusting her. She would also join The Doctor as another member of a Star Trek crew seeking to understand humanity, as she searched to reclaim her assimilated innocence.