The final general in Zaheer's Red Lotus was the one arguably the closest to him, the explosion bringing woman known as P'Li. Apparently, Zaheer had saved P'Li from an imprisoned youth, and she dedicated herself to him in thanks.
P'Li is eternally loyal to Zaheer and the cause, and as an "explosion woman" can send out massive explosions of firepower over long distances. Her only weakness is when the eye that shoots out the explosions gets hit.
In a cruel twist of fate, while dueling both Lin and Su, P'Li killed herself as the sisters wrapped a piece of metal around her head just before she fired a bolt.