Allah is Malik.
In the first Chapter (Surah Al-Fatehah), Allah T'ala says that He is:
مَالِكِ يَوْمِ الدِّيْنِ
The Master of the Day of Recompense. (1:4)
God will be the Lord of the Day when all generations of mankind gather together on order to render an account of their conduct, and when each person will be finally rewarded or punished for his deeds. The description of God as Lord of the Day of Judgement following the mention of his benevolence and compassion indicates that we ought to remember another aspect of God as well-namely, that He will judge us all, that He is so absolutely powerful, that on the Day of Judgement no one will have the power either to resist the enforcement of punishments that He decrees or to prevent anyone from receiving the rewards that He decides to confer. Hence, we ought not only to love Him for nourishing and sustaining us and for His compassion and mercy towards us, but should also hold Him in awe because of His justice, and should not forget that our ultimate happiness or misery rests completely with Him.