Be the death of somebody
Definition 1 of 2
Pro Tip 1/3Figure of Speech
Used to express frustration or worry, not actual death. 
Your tardiness is going to be the death of me!
Pro Tip 2/3Emotional Impact
Shows the speaker's emotional distress caused by someone else's action. 
This suspense is going to be the death of me.
Pro Tip 3/3Hyperbolic Expression
An exaggeration, not to be taken literally. 
Your constant joking will be the death of me!