What is the tone of the poem “A Poison Tree”?

The tone of the poem "A Poison Tree" by William Blake is dark, vengeful, and angry. The speaker expresses a desire for revenge against someone who has wronged him, and cultivates his anger like a plant in order to let it grow into a poisonous anger. The language is intense and confronting, with vivid imagery that evokes a sense of fear and danger. Overall, the tone of the poem is one of warning against the dangers of holding onto anger and resentment, and the destructive power of these emotions if left unchecked.