Underestimation

[Little_Girl]

to fail to guess or understand the real cost, size, difficulty, etc. of something:

[Jessica]

A judgment or rough calculation that is unfavorable or too low.

[Marquetta]

an estimation that is too low; an estimate that is less than the true or actual value

[CarinMusic]

Underestimation refers to the act or an instance of assessing someone or something as lower in value, quantity, importance, force, or significance than what is actually real or accurate. It often involves making a judgment or calculation that does not fully reflect the true worth, size, potential, or extent of the person or thing being estimated.