How to get rid of weird smile lines plus dent on dark chin? (Photo)

It sounds like you're dealing with several different concerns related to facial volume and pigmentation. Dermal fillers and fat grafting are both potential options to address these issues, but which one is right for you will depend on a variety of factors.
Dermal fillers are a non-surgical option that can be used to add volume to the face, smooth wrinkles, and improve contour. They can be used to address hollow under-eye areas, smile lines, marionette lines, and other areas of volume loss. One advantage of dermal fillers is that they can be done in a quick office visit with minimal recovery time. However, they are temporary and will need to be repeated periodically to maintain the results.
Fat grafting, also known as fat transfer, involves taking fat from one area of your body and injecting it into another area. This can provide a more permanent solution to volume loss in the face. However, it is a more invasive procedure that requires surgery and has a longer recovery time.
As for the dark pigmentation, this might not be addressed by fillers or fat grafting. There are other treatments such as chemical peels, laser treatments, and topical creams that can help with pigmentation issues.
It's important to have a thorough consultation with a board-certified dermatologist or plastic surgeon to discuss your concerns and decide on the best treatment plan for you. They can provide you with a comprehensive evaluation and discuss the risks and benefits of each option.

Fillers can help with the facial contours and adding volume to deeper lines. For pigmentation and texture concerns I recommend visiting a board certified plastic surgeon near you. You can consider chemical peels as well as medical grade skin care products, like Transform MD for improvement.