To what extent are the flaws in ontological arguments incapable of being overcome?

The key to answering this question is to maintain nuance throughout, with questions revolving around complex topics such as ontological arguments, a strong answer will rely upon a demonstration of subtlety and nuance. For example, a strong structure in exam will rely upon the assessment of strengths and weaknesses in the ontological argument, in a structured and measured manner. To achieve the top grade bands (A/A*) examples will also need to be demonstrated.
You may introduce the essay with a description of the ontological argument, before proceeding to highlight your first weakness. This could be the weakness in metaphysics, the very fact that ontological arguments rest upon no materially verifiable phenomena. Then you would demonstrate the mediation I have discussed, and introduce a counter, a ‘however’. This however, could, for example, revolve around an exposition of Anselm’s ontological argument for the existence of God. Logically and philosophically it succeeds in demonstrating a sound and logical defence of ontological arguments. An answer such as this would demonstrate mediation as well as knowledge (through Anselm) and, when developed, would be capable of achieving top marks.