Correct spelling for the English word "Riskful" is [ɹˈɪskfə͡l], [ɹˈɪskfəl], [ɹ_ˈɪ_s_k_f_əl] (IPA phonetic alphabet).
Attended with danger; hazardous; to run a risk, to incur hazard; to encounter danger; to take a risk, to assume danger; to insure.
Etymological and pronouncing dictionary of the English language. By Stormonth, James, Phelp, P. H. Published 1874.