Dreaming of an intruder at your front door with a knife on their back represents a fear or threat that is looming in your waking life. The front door symbolizes the boundary between your personal and public life, and the intruder represents an external force that is trying to invade and disrupt your sense of security and control. The knife on their back could symbolize a hidden or unexpected danger that you are not aware of. The fact that the intruder breaks in suggests that this fear or threat is becoming more pressing and urgent. However, the dream takes a surprising turn when you kill the intruder from behind. This could symbolize your ability to confront and overcome your fears and challenges, even when they seem overwhelming and intimidating. Killing the intruder from behind also suggests that you are using your intuition and inner strength to deal with the situation, rather than relying on external factors. This dream may be a reflection of your resilience and determination to protect yourself and your boundaries in waking life.