UltSans is extremely powerful and dangerous too, and can be only compared to high scale and not top entities of Marvel.
One of this entities, is Ghost Rider.
UltSans surpasses and overwhelms Ghost Rider in power, but that doesn't even matter as despite how strong UltSans is, is guilty of what he has done and feel guilty for it.
Ghost Rider's ability is very effective against him.
But now with the symbiot is way more effective, reaching more than being super effective against UltSans.
After the symbiot, UltSans got cleansed from his hatred corruption, and that guilt only increased extremely exponentially, making Ghost Rider's ability an instant win no matter what.