Assuming you mean Dota 2 I haven't played for some time but it used to be somewhat common 3 or 4 years ago for people to run scripts to instantly cast hex as soon as opponent appeared on their screen this effectively gave people inhuman reflex times.

You could tell they were cheating because if you watched replay from the cheaters point of view their mouse cursor would jump from current position to hovering over the target instantly and then immediately jump back to cursors original position all within a frame or two.