I have a deep dent across the top of my butt. What can help fill in the dent so I can have an even butt?(photos)

From your photos, it is difficult to tell if liposuction of the pre-sacral area alone would solve your issue, or if liposuction with fat transfer would be optimum.  I recommend being seen in person so you can be evaluated and discuss your options & desires.

You need a combination of liposuction and fat transfer to get the best result. I could not see your lower back area but you might could use some lipo there also to enhance the final look of the buttock. See a surgeon that has experience with lipo and fat transfer. Good luck.

Based upon your photo, i would recommend liposuction contouring of that area to sculpt down the area above the dent and +/- transfer that fat into the dent itself. An in person consultation with physical exam would first be necessary to confirm my recommendation. Glad to help.