A 'waifu' is by definition something with members, a certain appearance, combination of personal qualities, and proportions, and therefore a perfect 'waifu' is something which has these qualities in maximal degree.
But the qualities of such a 'waifu,' even if thought in their maximal degree, do not entail the existence of the waifu, for those qualities are merely modes of existence, and not existence itself. Insofar as they are distinguishable from existence itself, those qualities do not entail their own existence. Hence, the to hold the perfect waifu in thought does not entail its existence. The same goes for pretty much every other parody which attempts to use the ontological argument to prove some perfect qualifiedly-existent (and thus contingent) thing.
That than which a greater cannot be thought, however, has greatness simpliciter, and that in virtue of which beings in general are great, is the degree to which they have being. That than which a greater cannot be thought, then, has perfection of being. That which has being in maximal degree- that is, the most 'being-like being,' must have unqualified being- that is, actual *being* itself.
If an object of thought can be distinguished from actual being, then, it is not that than which a greater cannot be thought, and a more being-like being could be thought- that is, one could think of being itself. Since only being itself is indistinguishable from being, only being itself entails its own existence. Now being itself must exist, as Anselm realised, if we have a grasp of being at all (and hence, of the definition of 'perfection' in general), for if our notions of being do not ultimately refer to being itself, they are not notions of being at all. Only the perfect being, then, is such that if we have any notion of it, it must exist.
In short, your waifu a shit.
