Do I have a weak chin? (PHOTOS)

Thank you for your question. While you are not a candidate for a necklift, you would benefit by reducing the fat in your neck area so as to achieve a more defined jawline. Always work with a board certified facial plastic surgeon.
Best wishes,

"A formal evaluation would be needed to determine what's best. Many of my patients try to avoid surgery, so we perform a non-surgical chin augmentation treatment with injectable fillers. Fillers like Radiesse, Voluma, BellaFill as well as Sculptra are injected into the area, improving the overall appearance of the lower face and balancing the jaw and lip harmony. We use cannula injections to meticulously contour and project the chin, soften the chin along the jawline and improve the chin crease.

Implants are still a great option once you are 100% positive that you are ready for a permanent enhancement.​ I suggest getting a consultation with an experienced cosmetic dermatologist and facial sculpting expert; our practice is located right here in Los Angeles. Best, Dr. Emer"

I don't believe that you have a weak chin but you do have a poorly defined jaw line and lack of adherence of the submental skin. Botox would be of no use to correct this. You could expect an excellent improvement with liposuction of the submental fat, by a qualified plastic surgeon.

Botox would be of no use to you.  Chin implant surgery with liposuction of the neck would give you the best cosmetic result.  Consult with a board certified plastic surgeon to discuss your options.