A distraught mother needs fear to surpass her safety limit, but those at the ninth transformation can choose anger, greed for more power, or a pride that makes them always try their best to surpass their safety limit.
In the case of the Dominating Fire Force Intent, his limits will be removed completely by the emotion of Pride. It is not a baseless emotion either. It is an emotion fueled by the power of fire.
Any kind of emotion can work to break the limit, but that emotion must be sincere. The emotion must be real; it can't be pretended.
A woman can't pretend that her child is underneath a car and use that pretending emotion to lift the car. She must truly believe that her child is in danger, or she won't be able to overcome her limits.
Just like that, the pride in his excellence and superiority can't be fake. To make sure that it is not fake, its foundation is based on a real-life phenomenon of the domineering nature of fire.