John releases Arthur's leg as he feels his way up his other arm, so when the punch comes and knocks his head back and his mask askew, he is free to swing that arm into the one holding his throat.

He squints through the offset eyes of the mask at Arthur's face, and with his own face twisting up he digs his fingers into Arthur's forearm.

"Fuck you! I should have taken everything from you!" he growls.

Their positioning is... awkward, but John doesn't think beyond striking Arthur back, so he manages what he can with his left on the outside of this engagement - he swipes his palm at Arthur's head.