This scene perfectly captures two things. First, that Lust is more bloodlust than sexual lust. And second, how her sin (bloodlust) is a flaw of Roy’s.

Lust’s last words to Roy are that she looks forward the day when he’s “twisted in agony.” And there’s actually a subversion of what seems like sexual lust. She says that “being killed by a man like you isn’t so bad.” This might seem to be playing into Roy’s reputation, attractiveness, etc. But what she says after it makes it clear it’s not (“those eyes, looking straight ahead, unwavering”). She’s not admiring his attractiveness, she’s admiring his ruthlessness.

I think there are multiple parallels between the homunculi and certain characters (i.e. Greed/Ling, Wrath/Scar, Pride/Ed). And I think you can definitely see a parallel between Roy and Lust. When someone he cares about is threatened or harmed, he gets absolutely vicious, which you see in this scene (when Riza is threatened), but even more vividly in his fight with Envy. His desire for revenge is completely bloodthirsty, and almost leads him down a very dark path.

(via queen-of-twerking)