Scrambling a Rubik's cube by an adversarial noob
If the aim is to frustrate amateur solvers, maybe the best is to give them a configuration that seems very simple to solve, but will be hard with the common algorithms.
For instance you can just invert all the centers, or do a few swaps between squares, to have just 1 or 2 wrong on each face.
This is of course betting they don't know the special algorithms to create/solve these special configurations ;)