Learn English – “Destiny” vs. “Fate”

These words are related but might not refer to the same exact thing. For example if you check the Wikipedia entry for Authoritarianism you will find this entry:

Authoritarianism is a form of social organization characterized by submission to authority. It is opposed to individualism and democracy. In politics, an authoritarian government is one in which political power is concentrated in a leader or leaders, typically unelected by the people, who possess exclusive, unaccountable, and arbitrary power. Authoritarianism differs from totalitarianism in that social and economic institutions exist that are not under the government's control.

so immediately you see the distinction between authoritarianism vs. totalitarianism. If you now go to the Wikipedia entry for Totalitarianism you will find this entry:

Totalitarianism (or totalitarian rule) is a political system where the state, usually under the power of a single political person, faction, or class, recognizes no limits to its authority and strives to regulate every aspect of public and private life wherever feasible.Totalitarianism is usually characterized by the coincidence of authoritarianism (where ordinary citizens have less significant share in state decision-making) and ideology (a pervasive scheme of values promulgated by institutional means to direct most if not all aspects of public and of public and private life).

We see here that Totalitarianism is characterized by Authoritarianism AND ideology.

If we now check Despotism vs. Dictatorship we find that for Despotism is

a form of government in which a single entity, called the despot, rules with absolute power. That entity may be an individual, as in an autocracy, or it may be a group, as in an oligarchy. The word despotism means to "rule in the fashion of a despot" and should not be confused with "despot", an individual.

the key word here is "single entity" which can actually be an individual OR a group. Under dictatorship we find this entry:

A dictatorship is defined as an autocratic form of government in which the government is ruled by an individual, the dictator.

also we find the distinction between dictatorships and totalitarian rule (with reference to authoritarianism:

For some scholars, a dictatorship is a form of government that has the power to govern without consent of those being governed (similar to authoritarianism), while totalitarianism describes a state that regulates nearly every aspect of public and private behavior of the people. In other words, dictatorship concerns the source of the governing power (where the power comes from) and totalitarianism concerns the scope of the governing power (what is the government). In this sense, dictatorship (government without people's consent) is a contrast to democracy (government whose power comes from people) and totalitarianism (government controls every aspect of people's life) opposes pluralism (government allows multiple lifestyles and opinions). Though the definitions of the terms differ, they are related in reality as most of the dictatorship states tend to show totalitarian characteristics. When governments' power does not come from the people, their power is not limited and tend to expand their scope of power to control every aspect of people's life.

For autocracy we find this entry:

An autocracy is a form of government in which one person possesses unlimited power.1 An autocrat is a person (such as a monarch) ruling with unlimited authority.

a distinction is made between autocratic rule vs. miliatry dictatorships with some reference also to totalitarian rule:

Autocracy and totalitarianism are related concepts. Autocracy is defined by one individual having unlimited legislative and executive power, while totalitarianism extends to regulating every aspect of public and private life. Totalitarianism does not imply a single ruler, but extends to include absolute rule by any faction or class of elites who recognize no limit to their authority. Autocracy differs from military dictatorship, as these often take the form of "collective presidencies" such as the South American juntas. However, an autocracy may be totalitarian or be a military dictatorship.

I hope this helps! :)

Beyond the dictionary definitions, something that is

substantive

must have some substance to it, must not be trivial, must be meaningful. It is probably not simply pithy (on the short side), but still needs some support.

Something that is

substantial

needs bulk to it (in comparison).

That is, in quantity, 'substantial' is more than 'substantive', but substantive is not brief.

Another way to say this is that 'substantial' is a lot, and substantive has been filled out.