I got the achievement while using X-rays 2-3 times per step on the ladder. You just have to be careful to actually use the attack instead of blocking. Try pulling the left trigger before the right one to avoid any mistakes. --- PSN Screen Name: NoelVERMIIILLION X-Box LIVE Gamertag: Devouring Fang
Also, I remember accidentally pressing the block button during Shao Kahn's battle. I just knew I'd end up pressing it eventually since it comes naturally, however, I still got the achievement. I think you can press the guard button, but you can't block an attack from the enemy. If that's the case, there's no problem in using the special bar at all.
I was on beginner, too. I didn't get it the first time through, even though I was sure I didn't block. It might be safer to -not- do X-rays, but just keep in mind that it's possible to get the achievement while doing so. --- PSN Screen Name: NoelVERMIIILLION X-Box LIVE Gamertag: Devouring Fang
I just got it on beginner and I accidentally blocked a bunch of times, I just got lucky and never got hit while doing so. All that matters is that you don't physically block an attack, you can press the button all you want.
Also, if you press start when selecting your costume (after pressing start to bring up the option to select your costume) you'll pick that character's alternate color scheme. For instance, Stryker's is black and Scorpion's is orange. --- Gamertag: NXR Alpha X "The surest sign of immaturity is the never ending desire to appear mature." - Dude_bag