Wait...you have the "Combination Shock" achievement? Or are you trying to get it? Or have you unlocked the "Well Rounded" achievement, you mean?
There are 8 vigors:
-Murder of Crows
-Return to Sender
And there are 8 vigor combinations under the "Combination Shock" achievement:
-Murder of Crows and Devil's Kiss
-Bucking Bronco and Devil's Kiss
-Devil's Kiss and Charge
-Possession and Devil's Kiss
-Murder of Crows and Shock Jockey
-Possession and Shock Jockey
-Bucking Bronco and Charge
-Shock Jockey and Undertow
Thanks to KillerBEA for the sig!