WWE 12

I struggled with the initial solution, so here's how I got this...

First off, I chose HHH and played a one-on-one match against Santino.
Wear him down until you get your signature. When he gets up, press Y to perform the signature move (Spinebuster), and then immediately press and hold up on the D-Pad to perform a wake up taunt. This should make Santino stand up, then you should hit your finisher (Y), to perform the Pedigree.
After the move, just press B to pin your opponent and hopefully score yourself the three count, and 30 achievement score!

One of the easiest achievements in the entire game to get... basically when you get your finisher indicator, and your opponent is on the ground (Hint: after hitting a signature move, this is USUALLY the case) just do a taunt, they'll wake up and turn right into you... hit them with a finisher (Y) and pin them (B). If they're warn down enough, you'll get the 3 count and win. If not, beat them up a bit and try again.

Just beat up your opponent and wait until you have your signature move ready. Signature moves will do more damage.
After the signature move, your opponent should be down on the canvass, do the wake-up taunt then hit the finisher and you should be able to pin the guy. Watch the video for more details