Lust (ラスト)
Background
In the 2003 anime series;
Like her manga counterpart, she is highly intelligent, manipulative, and devoted to her own ideals; however, she begins to crave becoming a human as the series progresses. Her main purposes amongst the Homunculi are gathering information, and traveling to manipulate alchemists into creating Philosopher's Stones. Gaining true humanity is the focal point of her ambition, arguably much more so than the rest of the Homunculi.
In the manga and 2009 anime series;
Lust is the only female Homunculus and the second to be created by Father. Due to her high intelligence and devotion to Father's plan, Lust appears to have a great deal of free reign and authority within the organization, seeming to have a position second only to Pride and on par with Wrath. Lust also has a great disdain for humans, thinking them frail, predictable and generally stupid. Moreover, she appears to take pleasure in using and throwing them away. Lust is the first to introduce the idea of Homunculi as superhuman, the next wave of evolution of humanity, and takes pride in her nature.
-Taken in part from Wikia.