Fullmetal alchemist doesn't belong to me. If it did, there wouldn't be such a difference between the manga and the anime. It's almost as if they are two completely different stories, that only happen to have similar characters and plot elements.
She doesn't remember what it is like to feel pain. She regenerates so fast that deadly wounds heal before they even have a chance to sting. With a thought, her talons extend, piercing the heart of Gluttony's new snack. She almost envies the pitiful creature: envies him for that look of utter agony engraved on his face.
She's never mentioned this to the others. She wouldn't trust Envy even if she could throw him clear across the continent; Gluttony was to simple to even appreciate the concept, Greed was dead, Sloth too wrapped up in mothering Wrath, and Pride would report her straight to Dante. Well, Envy would too, but that was beside the point.
Maybe it was because she was named for the sin of sensation, that she, alone out of all the others, missed pain. She imagined the release of it, the cleansing chill, the pure focus demanded by pain's siren call.
She remembered once, not long after Dante found her, when she'd accidentally pierced Envy in the gut while training to use her 'nails'. The shape shifting sin had blinked, then knocked her violently to the floor with a single backhand, her nails retracting in reflex when he hit. She had struck the floor hard and fast enough to break a human neck, and it never even stung. Later, she'd asked Envy if getting impaled hurt, to be answered with rolled eyes, and a snort. There was no pain. Not for any of them. They all healed to fast for that.
It wasn't only pain she missed. She couldn't feel anything. The maximum that her rudimentary nerves allowed her to feel was the weight of an object she held in her hand or resistance as her talons pierced their target. Any other sensation, be it heat, or cold, or any physical sensation, was forbidden to her. All the others manifested their names in one way or another, with either their personalities or abilities. Greed's arivice had led him to turn against Dante not once, but twice. Gluttony was always hungry. Wrath lashed out in anger every time he was away from Sloth's emotional apathy for more than 2 minutes. Envy was consumed by jealously for the Elric brothers. Pride ran the puppet government. She was the only one who didn't manifest her name.
Sure, she had curves to literally die for, and sure, she dressed in such a way to make even the most experienced tramp feel shame, but if she couldn't feel, it meant nothing. No pain, no temperature difference, no physical sensation. She was Lust, the sin of sensation. Why didn't anyone understand that she simply wanted to feel?
Owari
Okay, little venture into the mind of Lust. I don't think that it is too far of a stretch to assume that none of the Homunculi feel pain at all. After all, Lust removes Hughes's knife from her eye like she's picking a rose, and the way she can stand and have Wrath shoot her in the face over and over again without flinching, she simply doesn't feel it. Sure, she can acknowledge a fatal wound, as she does with Marco, but she simply doesn't feel it. It seems to me, with how desperately Lust tries to become human, that there is more to that desire than to simply the will to die as Wrath accuses. After all, if Lust truly wanted to die, she could simply cut out her red stones, and she'd die. Something to think about.