Ultherapy ruined my neck. What can I do to improve this? (Photo)

You have a nice hyoid location and no significant fat to remove. You can see when you press up the skin touches the hyoid and you have a nice cervicomental angle. It doesn't need to be a deep plane necessarily but the platysma muscle will need to be tightened.

Sometimes the muscle can be overly tightened or deeper sutures may loop in some of the deeper neck structures. This is exceedingly rare but it has been described. This would require going back into surgery to release the muscle and/or scar tissue and/or sutures that may be holding the neck...

Your jawline looks fine. there is nothing that you need to do; this is normal and very much as tight as it can be from a surgical perspective; anything more would involve putting the skin on tension and will result in large incisions. If you are worried about skin stuff you should look into skin...