This is a wonderful poem by Sylvia Plath, who is known for her controversial and frank writing.
"Lady Lazarus" is often seen as as having many parallels to Plath's own personality and life. The speaker is sarcastic and bitter throughout the poem. Related to this, then, is tone.
Tone is the "mood" or "feeling" of a poem and its words. Just like tone of voice, writing also has tones that are made through the author's words.
Plath's tone in this poem is one of bitterness and revenge. Her "Lady Lazarus" appears as several different people, including a stripper and a sideshow freak. She is seeking revenge against a man, a father, whom she equates to a demon (eNotes).
Having taken up the battle with the enemy on his terms, she concludes by warning the male deity and demon that when she rises from the ashes, she consumes men as fire does oxygen. (eNotes)