1. Cruciatus Curse: This curse inflicts excruciating pain on the victim.
2. Imperio Curse: This curse allows the caster to completely control the victim's actions.
3. Avada Kedavra: This curse instantly kills the victim.
These spells are considered unforgivable because they inflict immense suffering and violate the fundamental principles of wizarding morality.
It's worth noting that the use of these curses is considered a major crime in the wizarding world, punishable by life imprisonment in Azkaban.