Abigail Lincoln

 Abigail Lincoln, aka Numbuh 5, is the second-in-command and espionage expert trained in stealth, information acquirement and fierce combat of Sector V of the Kids Next Door. In the end of the finale, Numbuh 1 made her the leader while he joined the Galactic KND.

Trivia:

 * Numbuh 5 and the rest of Sector V will join Barney in future adventures.