I'm sorry, but then... what was the big secret? This deviation from the comics?
<sighs> I hate it when people pretend to be obtuse. So god damned annoying.
Even in the comic, it was pretty obvious who Red Mist was from the beginning. Did that change the fact that his betrayal was shocking? No. Because it's a very common stereotype in the comics and fiction in general for the son of a crime boss to want to 'prove' himself by rebelling against his father. And that was a stereotype Christ was
using as part of his scheme, because he really
was a cunning mastermind. Even in the movie, the early scenes between him and his father showed that desire. The problem is, in the movie, they just came right out and told you what he was actually doing rather than
continuing to play up the fact that Chris was upset with his father constantly ignoring him and pushing him away from the family business.
Instead, they could have played up his own love for comics more. They could have skipped the whole "hey daddy, buy me these things so I can trick Kick Ass into letting his guard down so we can betray him!" scene -- that one, single scene is what really ruins it -- and just have him start showing up
exactly like he did in the comic. They could have had him run around with Kick Ass a little more, actually doing one or two 'heroic' things without Red Mist constantly sneering and acting double-crossy the entire time. They could have let him 'help' Kick Ass and Hit Girl sneak into the apartment complex and
then reveal that he was a backstabbing villain from the very beginning, and that the complex was an elaborate death trap.
It served no functional purpose to reveal all of that from the very beginning. It just made the character boring and impotent, and it made his final scene ridiculous and goofy. He went from a Lex Luthor type with a hint of genuine malevolence and cunning in the comic to a bumbling 60's-style Batman not-really-a-villain in the movie.