relentful
/rɪˈlɛntf(ʊ)l/rare
adjective
Sorrowful, softened, yielding, relenting. In later use humorous.
Origin
Late 16th century; earliest use found in George Chapman (?1560–1634), poet and playwright. Partly from relent + -ful, and partly from relent + -ful. In later use humorously after relentless.