There was a lengthy post/debate about that on GM last year, earlier this year (back hand or forehand), after the YEC. And after a long debate, it was a tie.
For me, it's her forehand, back hand, and the high lefty service out wide in the ad court (closer to the net), that the receiver doesn't even move for. It's almost like it turns on a axis/right angle, right off the court, so the receiver has no chance.
However, I also like the sharp two-handed back hands ROS she digs deep out the deuce court, then returns at the extreme angle (seemingly parallel to the net) for the ROS winner.
And I also like the off forehand ROS winner from the deuce court (that's close to her hip/body), that she just serves/spanks for a winner in the opponents deuce service box, like she's not even trying.
And I'll never forget that running, 10 ft behind the baseline, crouching, DTL--topspin forehand winner she hit at the YEC against Azarenka. Beautiful shot. Azarenka thought about volleying it. But Petra hit so hard, from so far, Aza only had a blink to think about it. But There were so many.
See that's how you know, Petra hasn't played nearly as well this year as last year. Cause I can clearly name you some beautiful/spectacular shot making that Petra made--especially on the run--when you didn't expect her to get to it, that she did last year, much more frequently than this year (if at all).
I'm smiling just thinking about it. I can't remember too many times Petra's shot making this year reminded me of last year or actually made me smile.
I know I mixed general (backhand, forehand, serve) with more specific shots/moments. So I'll stop there. Lol. But when Petra's on, her tennis is really a site to watch/behold. And she does it so effortlessly.
What about you? What shot's do you like?