Straightforwardly rhymes with:
awkwardly, downwardly, inwardly, northwardly, outwardly, upwardly, awkwardly, cowardly, dastardly, downwardly, good-naturedly, haphazardly, inwardly, naturedly, niggardly, northwardly, outwardly, upwardly
awkwardly, downwardly, inwardly, northwardly, outwardly, upwardly, awkwardly, cowardly, dastardly, downwardly, good-naturedly, haphazardly, inwardly, naturedly, niggardly, northwardly, outwardly, upwardly