Underestimated adverbs are provided in this article. The words listed here are commonly found along with the verb underestimated in sentences. This reference page helps answer the question what are some adverbs that describe or modify the verb UNDERESTIMATED.
badly, certainly, clearly, completely
consistently, easily, frequently, generally
greatly, grossly, largely, probably
seriously, severely, significantly, totally
usually, vastly
Hope this word list had the underestimated adverb you were looking for. In addition to adverbs used with underestimated, other example verb adverb pairings can be found on this site.
You can help by adding more adverbs in the comments. Thanks.