"He is the Rake..."
Another early Creepypasta for me, the Rake is a classic read. It details a humanoid creature that stalks (and kills some of) it's victims. This leaves the target with an increasing sense of paranoia, and justifiably so.
What's unusual about the Rake is that not everybody who sees it is immediately terrified; in fact, some seem genuinely concerned for it's well being. The pasta (which I highly recommend reading) reveals that he has been around since at least the late-1600's, and includes diary entries, a suicide note, and one entry (the bulk of the pasta) reveals what happened to a woman and her family.
She awoke in the middle of the night to see what looked to be a humanoid, dog-like creature sitting at the foot of their bed. Suddenly, it springs up and gets right in the husband's face, and just stares at him. It then runs spastically down the hall and fatally wounds their daughter. On the way to the hospital, the husband accidentally drives into a lake, killing them both.
The woman has since contacted others who have encountered the Rake, but fears that he is still watching her while she sleeps.
Spooky stuff. Reminds of when I was a kid and would sometimes be afraid that something was in my room with me (usually after a nightmare), and it happening to these people just drives that home. It makes you wonder whether something out there like The Rake might actually exist. Who knows? I'll let you be the one brave enough to search for the truth.