Off center chin "butt", could sliding genioplasty fix this? (Photo)

Sliding genioplasty is an extreme surgery that I don’t recommend unless you have functional issues. To fix the cosmetic problem of an asymmetric chin dimple, either a chin implant or repositioning the dimple would give you the correction you want. You must find an expert facial plastic surgeon to help you with this. I hope this helps.

 Hi, I have performed many facial shaping procedures, including Chin Augmentation with dermal fillers or silastic chin implants, for over 30 years.  A non smiling profile photo of your face would help in determining if your chin is indeed weak.  From the photo, the chin is a bit weaker on one side but a profile would determine if the entire chin is weak.  When the chin is weak, this creates an imbalance making the nose appear larger, the mid face top heavy, the lower face looks short, de-emphasizes the lips and allows early formation of a "double chin".  
 Proper placement of a silastic chin implant adds forward projection to the chin thereby creating harmony and balance to the lower face.  Using the same incision, liposuction can be performed to reduce the fat and further shape the neck.  Excess skin, from below the chin, can also be removed through the same incision.  
 I have found that placement of a silastic chin implant, through a small curved incision under the chin (also allows excess skin removal) to be very safe, quick, highly effective and far less invasive than a sliding genioplasty (requires extensive tissue dissection, bone cuts and placement of metal screws and plates to secure the cut segments of bone).  I perform chin implant surgery in 30 minutes or less, often using a local anesthetic alone.  If the chin is not weak but requires more volume on one side, precise placement of an HA dermal filler would be used to properly shape and augment that side. 
Hope this helps.