Deflate

Verb

1. To remove air or some other gas from within an elastic container, e.g. a balloon or tyre.
2. To cause an object to decrease or become smaller in some parameter, e.g. to shrink
3. To reduce the amount of available currency or credit and thus lower prices.
4. To become deflated.
5. To let (someone) down, disappoint them, or put them in their place.

   "deflate someone's ego"