No disagreements when decisions are made resulting in less conflict giving a single person the most power.
Form of rule that allows for balance and is much faster. When one person makes a decision, the process is much faster than having to go through several processes and branches in order to make a decision.
It has been proven that Monarchy actually provides for less corruption, everyone's used to following a single leader.
Cons-
Biased ruler. The single ruler might be extremely biased making unjustified decisions and hurting their people rather than helping them.
People have no say as they do in a democracy, if they don't like what decision was made, they can't do anything about it because they don't have a say.
A monarchy can decide to remove all checks and balances hurting the community.