i really, REALLY love how iron lung portrayed ava and simon as narrative foils
cause you have these two characters with an incredible amount of blood on their hands, and none of it is their own until the very end.
simon's primary motivation for almost the entire movie is just making it out alive. he doesn't care if the data he's pulling out of the ocean is important or not, he just doesn't want to die for it. he insists on being treated as a person, not a number. he's fighting for the individual.
ava, on the other hand, does everything in the name of humanity. she takes calculated risks. she's willing to let a few people die for the 'greater good.' she's fighting for humanity as a whole.
i think both of them feel guilt for what they've done but they have unique ways of avoiding it: ava dehumanizes the 'convicts,' and simon takes accountability away from himself. filament station "wasn't supposed to happen." he didn't mean to blast the crew with radiation. it doesn't lessen the harm, but it might help them sleep at night.
at the end of the film, though, their motivations get swapped!
ava, who's spent the whole movie fighting for the greater good, sacrifices herself for one individual.
by saving the blackbox, simon sacrifices himself to give humanity a chance.
and, in the end, they both take accountability for what they've done. ava learns simon's name (thereby humanizing him) and apologizes for what she's put him through. simon calls himself the butcher, accepting the title that's been placed upon him for his actions. it's a tragic ending but there's a lot of closure in it, which i really love.
one last thing that's been pointed out by others: ava and simon's respective names translate to 'the voice' and 'the listener.' how fucking cool is that?!