General Fear:
* Dread: A feeling of intense and fearful anticipation.
* Horror: A feeling of extreme fear and disgust.
* Fear: A feeling of anxiety and apprehension.
* Panic: A sudden, overwhelming feeling of fear and anxiety.
* Apprehension: A feeling of anxiety or fear that something bad might happen.
Extreme Fear:
* Fright: A sudden and intense feeling of fear.
* Trepidation: A feeling of fear and anxiety about something that might happen.
* Alarm: A sudden feeling of fear or anxiety.
* Panic: A sudden and overwhelming feeling of fear and anxiety.
* Agony: Intense physical or mental suffering.
Fear Inspired by a Specific Source:
* Awe: A feeling of profound reverence and wonder, often accompanied by a sense of fear or dread.
* Dismay: A feeling of disappointment and discouragement, often caused by something unexpected.
* Trembling: A feeling of fear or anxiety that causes physical shaking.
Figurative Usage:
* Reign of terror: A period of violence and oppression.
* Terrorize: To frighten or intimidate someone.
The best synonym to use will depend on the context of your sentence and the specific shade of meaning you want to convey.