The maori consider the treaty of waitangi unfair because

The Treaty of Waitangi was phrased slightly differently in English and in Maori, and in Maori it sounded like the British were not completely taking over the land, but only governing it and that the Maori would continue to have the ultimate authority over the land. Since the British understood the treaty as giving the Crown complete land to New Zealand, the Maori consider it unfair