Key revivals in Christian history have profoundly transformed the church and society, with significant events like the Welsh Revival and Azusa Street Revival leading to millions of conversions. Influential figures such as Evan Roberts, William Seymour, and leaders from the Great Awakenings emphasized repentance and intercession. The impact of evangelists like D.L. Moody, Billy Graham, and Chuck Smith further shaped the faith, highlighting the need for modern leaders to embody these qualities to revitalize the church and reach the lost.