I'm a bit late to the party but I would like to clarify some things (if possible) about the whole "guard break" and +12 thing. Actually I'd like to get away from the term "guard break" and go with the term "guard punish" for a moment...
Someone made a point that if you use akira's 2p+k+g, you can still block... this is true. After 2p+k+g hits on block, you will be at +12 frame advantage which gives you a big enough window to do akira's pk (since it fits in the 12 frame window) but you couldn't do 66p (which comes out in 13 frames)
using the move provides you with a guaranteed instance, but the recovery window is a lot smaller than say a guard break in King of Fighters or whatever.
Also, I should mention that you can not throw the opponent when a character is in this "guard punish/break" state.. if that matters
The problem with this discussion is probably an issue where nobody has agreed on a clear definition of the term "guard break"