Funny we'd have two sides of a debate then if everything was clear as crystal with no questions or problems, wouldn't you say?
When you look at the third film by itself, the second personality idea could have worked. But it's when you look back at the previous films and what had been established that the idea falls completely apart.
Xavier references in X3 that he put up the mental blocks to "isolate her powers from her conscious mind" and how the conscious Jean was always in control of her powers. The conscious Jean persona, according to Xavier, did not have access to the stronger powers because Xavier blocked them from her, an action that created the dual personality Phoenix.
We can conclude two important things from this. One, according to Xavier, the Jean Grey persona is always in control of her powers. And two, the removal of Jean's mental blocks would not only release the powers but also the personality, according to X3's explanation, since the personality was a direct result of the blocks and was hidden away with the powers.
However, in X2, in the museum scene, we see Jean incapable of controlling her telepathy and TK powers (she admits as much herself but also see the flickering televisions) with no mention or sign of this other personality. This defies the explanation provided, because we're seeing the Jean persona without control of these powers, and we're seeing the powers without the persona that supposedly goes with it.
Jean is tapping into these powers that were previously blocked from her consciousness, yet no sign of the other personality appears in the process. Nor does Xavier seem too worried about it, even though he knows full well that (1) he himself blocked these powers from her and (2) the other personality associated with these powers could very likely surface since he admits in X3 to having seen it in their private sessions.
Furthermore, when Jean calls upon these powers at the greatest level we've seen at the movie's climax, it's in an incredibly selfless and noble act - the saving of her teammates from utter destruction - and is the complete opposite of what this explanation tells us about the more powerful and rage-filled Phoenix persona. Again, no sign of the Phoenix personality even though Jean is readily and largely tapping into a vast amount of power that had, again according to X3, been blocked from her.
That doesn't even begin to try to explain the distinct differences in the manifestation of those powers. As Jean tapped into her stronger powers at the end of X2, there was a clear fire effect. She was surrounded in flame, and her eyes became red with fire. At the end of the film, the shape of a firebird can be seen on the water.
That doesn't appear anywhere in The Last Stand. Phoenix's powers are completely different and look nothing like what we saw in X2. She's sucking the life out of people with a black veiny look and demolecularizing them with no signs of any kind of fire manifestation that accompanied the previous use of this power. The fire that appears in the final battle is from the destruction taking place, not the kind of manifestation we saw surround Jean herself in X2.
Also, though this is rather minor in comparison, we're told in X2 that Jean could cancel out a mutant's power - Nightcrawler tells us that he can't teleport to get Jean from outside the plane because "she's not letting me." Yet as the Phoenix, to stay alive, Jean could have easily cancelled out Logan's healing factor and finished him off like everyone else. X2 tells us Jean/Phoenix has this power at her disposal, yet she for some reason doesn't use it.
You could argue that the Jean side of her wouldn't let Phoenix do that, but through that argument, you open the door to why the Jean side would have let any of it happen if she were strong enough to hold the Phoenix back from its power. Why would she let it kill Scott, the man she love and chose to be with in X2? Why would she let it attack Logan at all? By this explanation, endless more questions are raised.
And this is why it does not work, IMO. Not because of flaws it has standing alone, but the flaws revealed as part of the series. Because the writers (or whoever was responsible for this decision) did not tie the ideas together with what had been previously done. It's as if they were going off of a cliff notes page of what had happened in X1 and X2 rather than sitting down, watching the movies, and crafting their story to fit what had been established. And ultimately, in my opinion, this is why it disappoints.
Still think I haven't let it really sink in?
