Here's what rhymes with resoundingly.

Consider these alternatives

soundly / profoundly roundly / profoundly resounding / founding acclamation / relation nullify / high invalidate / state nullified / side invalidated / stated unsurprisingly / surprisingly voided / unexploited sensationally / educationally emphatically / automatically voted / noted repudiated / created rejected / respected plebiscite / might disproved / used reject / effect instated / dated nonbinding / binding confounded / unfounded