Knowing the meaning of both words gives us the answer to your question. Benevolent means showing or motivated by sympathy, understanding, and generosity. Omnipotent means having unlimited power. Putting it simply, God has the power to be kind and generous at all times, whether a person is good or evil.
This question raises the philosophical problem known as the problem of evil. If God is (i) omnipotent or all-powerful, (ii) omniscient or all-knowing, (iii) benevolent or all-good, and (iv) the sole creator of the world, then why is there evil in the world? The problem can only be resolved if at least one of these propositions is false.