Best way: If you installed it with a mod manager, uninstall it with the mod manager.
Second best: Got to the Nexus RealVision mod page, click on the FORUM or POSTS icon and ask how to completely uninstall RealVision. Different RealVisions install different files.
Third best: Locate your RealVision mod download and open it in 7-zip (or whatever) to see what files RealVision added when it was installed (extracted). Remove those.
Fourth best: If you just delete the ENB "d3d9.dll" file from your Skyrim directory, nothing in any ENB's will work.
Lessons learned: mod mangers make installing and, especially, uninstalling much easier. NMM will install (extract) loose file mod archives for you and allows for easy uninstall, especially if the mod overwrote any existing files.
Edited by Lord Garon, 22 December 2013 - 09:51 PM.