I understand that these are true:
• I can move my creature through my ally's, so l ong as i can fully pass their square.
• I cannot end my movement on an ally's square.
• My movement must stop once I enter a square adjacent to an enemy
So, can move through an ally's square if that square is adjacent to an enemy?
Pic: http://i.imgur.com/WOxF4to.png
No. Your third bullet point is incorrect. You can never* enter an enemy's space. Here's how it should read:
- You must end your movement as soon as you enter a square adjacent to an enemy.
Here's the relevant text:
"Creatures prevent enemies from easily getting past them. A creature must stop moving as soon as it enters a square adjacent to an enemy creature."
* Exceptions are Burrowing and Flying, but these still do not allow you to end your movement in an enemy's space.
My mistake. That's what happens when i write at work :/
I've corrected the OP to what I meant to say and linked the example picture better. I'm not talking about moving into an enemy's square. I meant moving through a square the enemy threatens, as shown in the picture.
The point still stands. As soon as you enter a square that is adjacent to an enemy, you must stop moving. You can never move into an enemy's square in the first place, excepting, of course, if you have the Burrowing or Flying keyword.
Using your picture, let's assign numbers to your Large ally. Top left is 1, Top right is 2, Bottom left is 3 and bottom right is 4. As soon as you enter square 3, you must stop moving, as it is adjacent to an enemy. But, since you can't stop there (as an ally is in the square), then you cannot make the move.