The opponents I hate playing most are the power loopers with heavy spin and pace. It's just annoying to deal with heavy topspin balls relentlessly making me move and block long. I like it when the ball slows down as my knees and my mobility are not as heavily challenged.
I'm sure you already know this, and probably implement it in your game already, but your best bet is to stop them getting the first loop in at all costs (touch their backspin serves and attack their topspin serves, whilst serving everything tight yourself) and if they do get in, use every drop of their juicy pace and spin against them with well placed blocks and counter-loops. Pin them down their backhand and when they inevitably turn to play a forehand, punch them out wide!
I have lost to a lot of people who cannot move that well, mostly because of their ability to use my game to their advantage!
Again, you may already know the above, but hopefully it can help someone else