I think Adam was the most important character

Very Bad Things has gained a reputation among those who have seen it as a tasteless, offensive movie. And it is just that. However, the movie is very self-aware of itself, and various characters and situations show that, while tragedy is played for laughs, there was usually some kind of conscience or karma present.

When the hooker was accidentally killed, Michael didn't jump up and hoot and holler at how cool he was-- he was genuinely somber over having played a part in taking someone's life. The other guys, sans Boyd, immediately showed concern as well, but Adam was the most concerned about doing the right things, insisting they called the cops to prevent the situation careening out of control.

And what happened when they didn't call the cops? The situation only got worse! As far as the hooker was concerned, her death was accidental, and they could have cleaned up the cocaine and said, truthfully, it was an accident. Worst case, Michael would have gotten manslaughter, and the rest, a slap on the wrist. But, having already decided to cover the incident up, Boyd committed cold-blooded murder on a security guy just doing his job.

Adam grudgingly went along, and during the burial, he insisted they rejoin the bodies of the deceased to give them a proper burial. It is played for laughs, yes, but it did show Adam was most willing to see the people killed as human. He continues to take what transpired the hardest, where the other guys simply tried to go on with their lives.

Adam pretty much died because he couldn't forget about what happened and how he would never be able to let it go. When Adam dies, the movie itself doesn't die, but the conscience that was present pretty much did.

After Adam's death, his confession to Lois led to Boyd killing her, and Michael's pledge to come clean, which led to HIS death too.

"Look at that big, blind, gawking b**** boy."

Really, look.

Never hate your enemies. It affects your judgment. -Michael Corleone