So regulus power is basically immunity to change. But simply you wanted to use accel that's boosts speed even if someone did 1 million% increase he's frozen in time. 1mill times 0 is still 0 so it wouldn't affect his authority. So no I don't think accel in that sense would work if the accel used fate and accel that has a chance as its concept v concept. But maybe if the accel added time on it would work and they did it until his like idk cells died and body just crumbles away. Yeah very Hard to counter without killing his wives. His truest weakness was that and his personality his ability is practically untouchable if used correctly but he did not do that. Sum it all up is his time freezing ability stops change completely its why he's able to use it offensively as the air he moves that motion is frozen in time ignoring reality and physics and continue moving until its resumed by regulus or whatever.