Eat somebody alive
Definition 1 of 2
Pro Tip 1/3Emotional Intensity
This phrase conveys strong negative emotions; used when someone is upset or angry. 
If you mess up this deal, our manager will eat you alive.
Pro Tip 2/3Informal Context
It's informal and often found in spoken language or casual writing. 
You better be prepared or the audience will eat you alive.
Pro Tip 3/3Hyperbolic Nature
The phrase is hyperbolic, meaning it exaggerates the severity of the criticism. 
Show up unprepared, and the critics will eat you alive.