Across various competitive arenas, from sports to warfare, the principle holds that a failure to respect your opponent's abilities can lead to your own defeat. It is important we shpuld never under-estimate the power of an enemy. An enemy be it at any level always try to get an upper hand on us. We should remain alert about their next course of action. To convey this all important message, Sanskrit says ;
अल्पोSपि ह्यरिरत्यन्तं वर्धमान पराक्रमः |
वल्मीको मूलज इव ग्रसते वृक्षमन्तिकात् ||

Alpopi hyariratyantam vardhmaan paraakramah. Valmeeko moolaj iva grasate vrukshamantikaat.
Alpopi = alpa + api.
Alpa = a little, small.
Api = even.
Hyariratyantam = hi + arih + atyantam.
Hi = surely, because.
Arih = enemy.
Atyantyam = excessive, quite.
Vardhamaan = by growing.
Paraakramah = power, strength.
Valmiko = white ant, ant hill.
Moolaj = grown at the root (of a tree)
Iva = like (for comparison)
Grasate = swallows, devours.
Vrukshamantikaat = Vruksham + antikaat.
Vruksham = a tree.
Antikaat = from the proximity.
i.e. Even if an enemy is very small, after some time their power increases tremendously and ultimately they creates a threat to their very existence. Just like a small anthill located near the root of a tree slowly eats up the entire tree.
We should never underestimate an enemy because underestimating them can lead to overconfidence, complacency, and a failure to properly assess their strengths and weaknesses, ultimately increasing your risk of defeat. Underestimating an enemy prevents you from learning about their strengths, weaknesses, and strategies. Citing the examples of anthill the proverb indicates the power of small ants who by tunneling into a decaying woods. They create a physical weakness in the tree, or by providing a breeding ground for fire ants that can damage roots and bark.