I'm trying to translate into latin a prayer in which the Virgin Mary is asked "to render all spirits impotent, paralyzed and ineffective in attempting to take revenge against anyone of the members of the Auxilium Christianorum [a religious association]", but I have problems with this "anyone of the members", beacause I don't know which indefinite adjective or pronoun should I use. I've always found difficult to differentiate between the many different indefinite adjectives and pronouns in latin (ullus, quivis, quisquam, etc.). Should it be "ullum membrum", "quodvis membrum" or other, or is it indifferent?
Very simply, the situation is this:
In positive sentences, you say quis, aliquis, quispiam, quivis or quilibet. These all have their adjective forms as well, which are largely the same, but differ slightly (aliqui, aliquod and so on).
In negative sentences, incredulous questions, condicions unlikely to be true, and comparisons with quam, you use quisquam and ullus, where the former is generally only used substantively, the latter only adjectively.
You can roughly think of quisquam/ullus as meaning "anyone ever, anyone at all." Si quisquam, ille sapiens fuit = "if anybody was wise at all (but I doubt it), it was him." You could write something like: si ullum membrum ulcisci conetur; but the meaning would be more like: in the unlikely case it should take revenge on anyone at all... which is not really intended.
So essentially you want one of the "aliquis & friends" group. The difference between aliquis and quis is subtle, but the gist seems to be that aliquis assumes the existence of someone/something without specifying him or it further, while quis does not and talks only about the possibility that there could be somebody. That is why it is regularly used in condicions (si, nisi, etc.), ne clauses and num questions, but also often after cum and in relative clauses. Quispiam is very similar to quis, and quivis and quilibet mean "anyone, no matter who, whoever it may be" etc.
You are talking about a theoretical case, probably using si or a relative, so I would avoid aliquis, and a simple answer would be: qui quod membrum nostrae societatis ulcisci conetur or some such.
However, in English, you would not need an indefinite pronoun at all, you could simply say "against one of the members," so I guess you want some emphasis here. Therefore I would say:
... tarda et frustrare quemque spiritum, qui quodvis membrum Auxilii Christianorum ulcisci conetur.