Flechette and Weld don't know how he thinks he can defend against her power, they just know it was difficult.
"It is literally impossible for a power to be any stronger than that without fundamentally altering the mechanisms by which parahuman abilities operate or changing the underlying mechanics of reality."
Lily didn't know what was more frightening, the fact that Apeiron was completely confident about the strength of her power, or that he was talking about alteration of the function of powers and the mechanics of reality as if they were actual options for him.
"My power, it would be strong enough to hurt you?" She asked. It felt intrusive and in bad taste, but that was what he had been implying. She couldn't leave things without confirming that.
Apeiron made a nebulous gesture. "A week ago it would have been." He said casually. She and Weld just looked at him. Weld managed to recover from the impact of the statement first.
"You said it was the strongest power in the universe. The strongest possible power." He said.
"It is." He said with a nod. "You would not believe the bullshit needed to properly defend against something like that."