Reaction videos where they basically show the whole video/trailer and then their reaction either after the video or face-cam during the video are the worst. The monster views come from the people wanting to see the video/trailer in question, not really caring what the guy thinks, but he still got the views.
The only 'reaction videos' I like are rants, thoughts, or discussions about the video, but without actually showing the video in question. If I want to see the video, I'll go see it myself. I watch those videos because I want to see their thoughts and/or rants about it. The other kinds of videos that actually show the video/trailer in question should be taken down for copyright.