Dark Knights aren't necessarily dishonorable or manipulators. Going by the description here, they're the guys who hunt down corrupt members of the clergy and aristocracy when the law can't. Grit seems appropriate for anyone whose goal involves going against some of the most powerful people in a society no matter what the consequences are (like becoming a pariah or feared). Think like Batman or Daredevil with a great sword. I think Grit pretty much works fine, but the loc team has been known to make weird changes (maybe the original Japanese is better/has a different nuance), so who knows.

As far as the emo thing goes, my Japanese is pretty bad but I'm fairly certain Yoshi-P used an expression that doesn't have a good English equivalent, and "emo" is kind of the closest fit. Think like a teenager going through the whole "look at me I'm so badass and cool and such a tortured soul. I fight against these horrible oppressors even though no one will ever know about my struggle and pain. I'm so badass and cool." Seems to fit dark knight/batman/daredevil lol.