Would 'λυπάμαι για το θύμα' work?
yes it would(i do not know if duolingo accepts it as an answer though) and it is more natural ....
Thank you alepouditsa! Much appreciated. I was marked incorrectly for it, but wasn't 100% sure if I was right or not. I'll report it if and when I come across it again.
Added! :)
Thanks Troll!