Most S/V are good at reading the lob and moving back to cover/attack in my experience.
Counter with a 2 point pass. First ball low to their feet, preferably with pace. Step in and take the reply safely down one of the lines depending on your stronger stroke....or just take their head clean off, hammer the forehand shoulder which will jam them if they get the racquet there in time.
First ball not good enough? Just like a net exchange in doubles, keep their contact point low and below the tape as you move in, attack the first high ball.