One of the reasons that Douglas comes off well is because he has 2 actors playing his partners who seem very different from him. Andy Garcia is great as Douglas' fellow officer helping to transport a crime lord back to Japan. When most people think of BLACK RAIN it's usually Garcia's final scene that pops in their head. It is a brutal one to be sure but it hits the audience so hard because we genuinely like the guy. What also makes that moment effective is Douglas' powerless feeling during that scene. He sees all of the action play out in front of him and there's nothing he can do about it.
Aside from Garcia, Douglas has a lot of great scenes with Ken Takakura as a Japanese cop who acts as a liason to Douglas and Garcia. The moment that Douglas confesses to Takakura of taking drug money while in New York is very effective and makes you understand why Douglas makes a very important decision during the film's climax.
The movie looks real sharp and I suppose a lot of the credit for that should go to Jan De Bont who served as the director of photography. Hans Zimmer's score also does a great job of setting the film's moody atmosphere. But ultimately it's Ridley Scott who deserves most of the praise for BLACK RAIN. It's truly an underrated film from a guy who has made so many quality flicks.