What makes a one party system so dangerous to implement?

The one-party system refers to the political frameworks where one party forms and runs the government. It can happen in two ways. Either the activities of the opposition can be outlawed or the possibility for the opposition to come into power is suppressed. In some cases, the dominant parties allow the less dominant ones to exist, so that the party can hide authoritarianism. Some scholars argue that even in multiparty system party can act as authoritarian, so the legal framework, social and economic and political factors become important in such matters. The one-party system is dangerous as one party nominates all the candidates and there is no place for opposition.

it increased the power of the king of england.