I've searched just about every SC page there seems to be ..

I can't do friggin critical strikes.

*One piece of armour destroyed.
*They are in soul crush, red flashing
*full blue flashing on my side

That's what my opponent is like, and thats what every SC page says they need to be like

I've tried both pressing it just once and rapidly tapping, right up next to them like a throw, and away.

Nothing seems to work.

I am on level 45 or whatever in the Tower and I am about to rip of my own head.
I am getting very pissed off, I think I remember why I stopped playing video games I am one of those people that get frustrated so easily.

(Another thing unrelated that annoys me about this game is when your teammate comes in they RUN RIGHT IN FRONT OF THE PERSON and before you can even do anything, the computer is in mid swing of a powerful hit WTF)

I don't feel like registering on some other gaming forum for SC so hopefully someone here knows the answer.

and my cerventes variant pwns people on live.

First, check your controller settings, and make sure the left bumper/L1 button is set to A+B+G+K.

Enter a fight. Once an enemy their soul gauge is depleted, you need to get them into a vulnerable state (most often, it's when an armor is destroyed and it makes a red "splash"). On either Xbox 360 you need to hit the left bumper, or on PS3 hit L1. I usually hit it three or four times very quickly, just to be sure.

To practice, hit it the button under normal circumstances (full soul gauge), and your character should put their hand on their head like they have a bad headache.

The best person to cause soul damage is Yun Seong. Use the Dragon Sword, and hit Forward Y, Y.

Yup, they do that hands on head thing (I've tried both just hitting all 4 buttons on the LB they are the same)

Do I need to do the soul damage / armour damage in a order? Time anything?

Once their orb and soul gauge are flashing, bust off some armor (to make the red "splash", then immediately tap the button. It needs to be very, very quick after the splash (~.5 seconds).

I'm about to jump on Live right now if you care to play, though I'm not very good.

ProfessorSteven

Also keep in mind that if you do ANY attack after they are soul crushed, you will not be able to do the critical finish. The critical finish must be the very next move you do after soul crushing.

And you do not need to break armor to create the black/red flash needed to do a critical finish. It just needs to be a hard hit, usually a stun attack will do this.