“Interfere” means to intervene in a situation without invitation, usually in a disruptive or unwanted manner.
Option A: "counter" — Not directly opposite; it means to oppose or respond to.
Option B: "assist" — This is the opposite, implying help or support rather than obstruct.
Option C: "hate" — Unrelated in meaning.
Option D: "fight" — Could be related to interference but not an antonym.
Therefore, assist is the correct opposite of interfere.