Okay so I’ve got a few paragraphs down, but I need some more ideas. What are some advantages and disadvantages on having an all powerful King? We’re talking about middle ages, here.
Well aren’t you two assholes helpful.

An all powerful king prevents civil war, there’s no other leaders to go up against
Also the kingdom is probably more united..
Disadvantages are the kingdom is run under only one persons point of view, may not be what’s best for the people.
Or there’s a fine line between monarchy and dictatorship sometimes all powerful kings cross it…
Hope this helped.