The One Punch Man addon is a one punch kill modification. No matter which type of item you have in your hand you will always make 600 attack damage which is more than enough to one shot any type of mob in Minecraft. For example, you can use this mod to instantly kill the Wither Boss or easily fight your way through a horde of zombies.
Horses are normally quite difficult to slay but no more! I admit that it’s not fair to kill horses as they are very friendly. I would much rather want you to use this ability against hostile mobs, e.g. zombies and alike.
To really demonstrate how this looks in-game an image doesn’t really help much. That’s why I put together this short video down below which demonstrates how it looks in-game.