Meh. Manages to somehow be generic and exaggerated at the same time. 6/10.
The MC is underestimated to the extreme, but is actually overpowered to the extreme.
He looks down on the hero party like they're squabbling kids.
Everyone else is so incompetent it's a wonder they're alive.
Also he's basically rich enough to buy the kingdom and spends money lavishly.
Look, there's a limit where you lose suspension of disbelief even in a power fantasy.
This manga crosses that limit, but does not go far enough past it that it actually becomes funny.
Overall, there's better manga I could read.