Answer: If you underestimate your opponent you have automatically put yourself in a great danger. Your opponent should not be underestimated if you want to be successful. Not underestimating your opponent will give you reason to be prepared adequately, with that attitude you win always.
If you underestimate your opponent it would be difficult to prove yourself, you won’t know what you are capable of achieving, for example a soldier is not expected to under estimate an enemy on the battle field because if he did, he won’t be prepared adequately to face the battle.
Another example is a popular boxer Anthony Joshua who lost a fight to Andy Ruiz Jr because he underestimated him.