These curses are awful and, as I have said many times, should NEVER be used! But, why do I keep saying not to? Why are they actually so bad? Well, these curses can do so much damage to one's body and could seriously injure someone. Even though they may not all sound so bad, they are called unforgivable because they are the three worst curses in the wizarding world. The killing curse - is self explanatory but I'm still going to tell you - can kill someone with just a simple flick of the wand and the correct incantation. I don't know if it is (I assume so), but I would say that the killing curse is the worst curse ever. Another killing curse is: Sectumsempra - which Severus Snape invented in his youth to use on his enemies. These, to me, are the worst curses possible as they can kill instantly. To be honest with you, I don't know why they were ever invented. The Imperius curse is a controlling curse which, if used on a fellow human (witch, wizard or muggle, it does not matter), gives you instant control over their body. Many Ministry Of Magic workers were put under the imperius curse during the year of the Battle Of Hogwarts so the Death Eaters could take over the Ministry. However, if the person who has taken over the body dies, the body would be freed of the curse. Also, the cruciatus curse is probably the second worst curse in the wizarding world as it allows the witch or wizard to torture the victim. This could end up very unfortunate to the victim as it is possible to kill them.