Just finished watching Bad and Crazy. It's one of my first k-dramas ever and I have no idea where to go from here. The thing that struck out the most was how awesome the two main male characters relationship was and how much fun, action, insanity, etc was packed into their interactions. I don't think a focus on this type of relationship is common, but if it exists anywhere else let me know. 

Hi, my country: the new age sounds like something that might interest you. It has an amazing bromance between the two male leads. Their relationship was so beautiful to watch for me. The best bromance I have seen. It's a historical drama that has a bit of everything, including action and a little bit of romance. give it a chance, please; you might end up loving it.

All mentioned beneth are historicals

I second My Country New Age.  On my part I  reccomend  Worrier Baek Dong Soo .  In both of these dramas bromance is epic and a central relationship and emotional core but  mind that these two are very angsty, often heartbreaking bromances. There is also plenty of heartwarming bromace(s)  in: Rebel:Thief who stole people, Chuno: Slave Hunters,  Hwarang ( this  one is a lighter, fun  drama) , Acient Detective