[1Sa 15:19-21 KJV] 19 Wherefore then didst thou not obey the voice of the LORD, but didst fly upon the spoil, and didst evil in the sight of the LORD? 20 And Saul said unto Samuel, Yea, I have obeyed the voice of the LORD, and have gone the way which the LORD sent me, and have brought Agag the king of Amalek, and have utterly destroyed the Amalekites. 21 But the people took of the spoil, sheep and oxen, the chief of the things which should have been utterly destroyed, to sacrifice unto the LORD thy God in Gilgal.
Not really a genocide if the king and others were kept alive though, was it?