Fate/Zero, Hunter x Hunter (2011) Recommendations
Shounen battle shows that spend more time talking about ambitions, rules, and mechanics than actually fighting, making the plot and action even better since the viewer fully understands the importance and consequences of every move the characters make.
Similar dark setting with lots of strategic battles and an equaling amount of brutality-- perfect choices for those who are fans of grey and gray morality series. Also, there are a lot of likable and interesting characters in both series-- feel free choose your favorite.
If you're a fan of fights with strategic thinking then these two are for you. Most characters in both these anime are smart and cautious. Both anime have very good quality production.