Grieve (Grieved) God grieved when He seen how evil mankind had become:
And God saw that the wickedness of man was great in the earth, and that every imagination of the thoughts of his heart was only evil continually. Gen. 6:5
God's heart was grieved because of the evil that man had become.
And it repented the Lord that he had made man on the earth, and it grieved him at his heart. Gen. 6:6
God decided that it would be better to destroy man and all living creatures because his grief was so great.
And the Lord said, I will destroy man whom I have created from the face of the earth: both man, and beast, and the creeping thing, and the fowls of the air; for it repenteth me that I have made them. Gen. 6:7
There was but one man who found grace in the Lord's eyes and that was Noah so God decided to destroy all but Noah and those He instructed Noah to put in the ark.
But Noah found grace in the eyes of the Lord. Gen. 6:8