[The_Rorschach]

"How can 'God' be both all good and all powerful?"

Read Isaiah if you ascribe to Christian or Jewish theology, if you do not, be more precise in which god you are speaking of.

God said to have created both good and evil, taking responsibility for both. Life, without free will, would be meaningless. Essentially, he is Good because he chooses to be responsible in the use of his omnipotence.