And if you've taken all the prisoners inside
if someone takes no prisoners, when they try to achieve something they are very determined and do not care about other people’s feelings. the opposite of this means you care too much about others feelings and haven’t been ruthless enough. Maybe hes saying the subject cares too much about feelings of her own and of others.
To help improve the meaning of these lyrics, visit “50/50” by The Strokes Lyrics and leave a comment on the lyrics box