This is the best way to stop a hacker in Dark Souls 2:
Source: Oroboro the Ninja, Hacker Exterminator Extraordinaire:
The best way to stop a hacker is to employ gravity. Everyone is subject to gravity. Just knock the hacker off of a cliff before they can stop you, or attempt to banish them in some other way.
Source: Marshal "Lumpy-Head" Jahnke