The killing curse; Avada Kedavra. Kills the victim instantly. Very nice explanation Miss Yvette! 5 points to Slytherin! And, as you said, the unforgivable curses are some of the most powerful. In fact, they are the most powerful spells know to witches and wizards. Yes, you must really mean these curses in order to achieve performing them correctly.
The torture curse; Crucio. Very good description Mr Telvanni! 5 points to Gryffindor! This curse causes very intense pain to the victim and if the curse is powerful, or as you said, its duration is long, he or she can be driven into insanity.
The Imperius Curse: Imperio. This curse gives the caster complete control of the victim. It is indeed possible to resist this curse, but it is very difficult and great force is needed in order to do so. Out of the three unforgivable curses, the imperius curse is the only one that can be resisted.
The leg-locker curse, which can be performed using te incantation Locomotor Mortis, causes the victims' legs to lock together. Its effect is similar to the one of the body bind curse, Petrificus Totalus, which freezes the victims' body.
