Question

show that the monopoly will never produce any desirable outcome

Answer 1

A monopoly always have a lot of disadvantages. Its disadvantages are far more than its advantages therefore it never produce any desirable outcome.

Usually a monopoly has no competitors at all so it can influence the prices of a product or a service or both according to its will. So usually it charges the prices more than the marginal cost  of a service or product.

It usually happen at the start of a venture when there is no competitor for that specific product or service.

So it only benefits that particular organization and creates an unbalanced price and cost ratio. And these higher prices reduces the number of customers. So the profit for a monopoly cannot be considered as Unlimited.

So it will not produce desirable results in any case.