The speaker begins by naming what another person does: you bother me, your person bothers me, your acts bother me. It sounds like simple irritation. But by the fifth line the poem turns inward. All that bother makes the speaker feel like a bother too, and the word keeps repeating until it stops describing the other person and starts describing the speaker.
The key shift comes with the word "toxicity." The speaker says it "kills" them, which suggests this is more than annoyance. It is the slow wearing-down of someone treated as if they are always in the way. By the end, the speaker has absorbed that judgment completely: their actions, their feelings, even their whole person are "the bother."
The mood is raw and quietly painful. The plain, repetitive language feels like a thought looping in someone's head, and the ending, with no comfort or escape, leaves a sense of lost self-worth.