the hardest ball to catch is a line drive directly at you. because you can't tell the linear velocity(i think thats the term). when the ball is hit to your left or right, you can estimate its velocity, acceleration, and angle where it might land. a ball directly over your head is somewhere in the middle.. this is why in the majors you see guys drifting to the ball,, even though 95% of coaches teach you to get under the ball first -but that just makes it harder to catch.
you really cant say there is a greatest catch because theres so many variables. a routine flyball that gets lost in the lights is just has hard as an over the shoulder. i think the best catches are when you sacrifice your body. like guys slamming there heads into a wall.
