Height of the bounce and depth of the shot are a pretty big deal at this level. The absolute worst for someone with a weak back hand (read most 3.0-3.5 players) is a looping topspin with some depth. They cannot really just block it back and that causes problems that can't be solved in a match, on the fly. The result is very often an UE, or a very weak return that lands limply in the middle of the court, begging for a volley, drop shot or a wide angle put away. If someone is able to block back shots with pace on them, do something different. That is not any kind of great insight or deeper level thinking, I realize.