How to counter aggression

I have a friend who always uses a slow, long pendulum sidespin+topspin serve. He plays REALLY aggressively and is able to perform any attacking stroke quite consistently. I am able to attack his serve, but he just counters it back with even more speed and power. Keeping the ball low and short doesn't work either because he is really good at flicking. What can I do against him?

Hi Jack,

I would try variation of speed and placement.  Even playing a slower topspin may be the answer.  Also keep changing where you are playing that shot to.