One of the more darker unicorns that I came up with for this series.
Radioactive Unicorns are a sad byproduct of a nuclear explosion, caused either by an atomic bomb, or a failed nuclear reactor (think Chernobyl). Some of these unicorns are essentially a walking Elephant's Foot, and are therefore unapproachable. Unfortunately, driven mad by radioactive sickness and sheer isolation, these unicorns do not understand the danger they present to their own surroundings. Being a creature that seeks to aid something like a wounded animal, they fail to understand how they only cause more harm. Special rangers are assigned to keep an eye on these unicorns, to try and make certain they don't come near human settlements, but it's very lethal, leading it to be a constantly rotating position.
The most merciful thing would be to somehow end the misery of these poor creatures, but scientists have yet to discover a way to do this.