the element of irony in Lustâs death is complicated by a few factors, i think, including firstly that she died first before the pattern was set up, but more importantly that her relationship to her name-sin was different from those of the other homunculi.
unlike her brothers, thereâs no evidence sheâs herself particularly susceptible to the impulse sheâs named for. which can in Doylistic terms be largely attributed to Arakawa following an existing sexist set of types for depicting the Seven Deadly Sins, but in-setting we can take as indicating that acquiring a human body did not make Flask Homunculus particularly horny, or at least not particularly inclined to aim that at anyone. (ace villain mood possibly lmao.)
instead the self-element he expelled for the concept of Lust seems to revolve mainly around the capacity to be sexually wanted and objectified by others.
when Lust dies, itâs directly because of the casual murder attempt she made on someone sheâd weaponized her desirability against, in the attempt to manipulate his feelings for information. itâs because she stabbed her disposable fake boyfriend.
she doesnât die because of what she is, or because she went up against Roy Mustang, or because she underestimated humans, or because of her fatherâs plans, or anything like that.
Lust dies because she does not respect the way people care about each other, doesnât understand it, regards human relationships in zero-sum terms and affection as something to exploit.
Lust dies because while she didnât love Havoc, not in the most infinitesimal degree, somebody did.