This is a video of Youtuber Giaco Whatever adding razor blades to a high performance yo-yo to see what kind of damage it can do (previously: his lawnmower blade blender). I would say it's only capable of moderate damage -- slicing through several hotdogs, a tube of Pepsodent toothpaste, and a bag of flour. Unfortunately, it didn't quite have the same oomph as Rygar's yo-yo weapon from the classic Nintendo game. I destroyed so many monsters with that thing. And, okay, maybe my own penis when I was first getting the hang of it. Whatever, those old NES classics didn't hold your hand through the first few levels like today's games.
Keep going for the video, but skip to 3:10 for the actual testing to begin (immediately following an ad for a smartphone video game).
Thanks to Ben J, who agrees it would have been a lot cooler if he actually threw the yo-yo by hand.