the polynomial must be even, so we chose x²
it has at least 2 terms, then we add 1 to the previous item, we get: x² + 1
to get outputs larger and larger in the negative direction, we have to multiply the previous item by -1 to get: -x² - 1
This function has a graph like the next one:
Then, -x² - 1 satisfies all the features needed