To be blunt: shut down the attack or slow it down and redirect it AND get the hell... out... of... the... way.
Strike the attacking arm (in this case) while getting off-angle, create space, and get to a position of advantage.
Leverage environment for protection if possible, get to your equalizer or continue to create distance and regain the initiative... quickly.
Test it. Refine. Test your skill again. Repeat.
BUT if you don’t adamantly train to develop the performance of maneuvering dynamically offline of the attack, striking with speed and power, etc., this scenario will turn quite ugly.