Friend, Our Legend --- Drama version of classic gangster film
Friend --- the original movie
Not Exactly what u want, But Close!:Chuno --- Great bromance ... not exactly gangster, but outlaws, etc...
City Hunter --- Interesting father-son dynamics
East of Eden --- Gangsters, family dynamics, lost brothers ..... Bromances that rival the romances .... Not typical melodrama due to exceptional writing!
IRIS -- Secret Agents not gangsters .... weak bromance but interesting relationship and friendship dynamics .... similar to Time Between Dog & Wolf
Movies:A Better Tomorrow --- Gangster bromance and brotherhood
Guns and Talks --- comedy gangster bromance