When searching for antonyms for the phrase "regard highly," words such as dislike, despise, or condemn will come to mind. Some other suitable options may comprise belittle or devalue, which essentially connote the opposite of having high regard or respect. Discrediting something or someone shows a complete lack of appreciation for their value or worth. Additionally, overlook or disregard would be choices, implying that the subject at hand is either deemed unimportant or not worth considering. Overall, these antonyms denote a negative perception, undermining the esteem or significance attached to the presiding entity.