Retarded adverbs are provided in this article. The words listed here are commonly found along with the verb retarded in sentences. This reference page helps answer the question what are some adverbs that describe or modify the verb RETARDED.
actually, considerably
greatly, materially
mentally, mildly
probably, profoundly
seriously, severely
slightly
Hope this word list had the retarded adverb you were looking for. In addition to adverbs used with retarded, other example verb adverb pairings can be found on this site.
You can help by adding more adverbs in the comments. Thanks.