"I'm so angry I want to [insert expletive or very violent action]."
You are aware, aren't you, that that's probably a mis-use of the word "expletive"? Unless you mean the post-Watergate non-linguistic meaning of "bad word".
"The linguistic meanings of "expletive" come from the Latin verb explere, meaning "to fill", via expletivus, "filling out". It was introduced into English in the seventeenth century to refer to various kinds of padding—the padding out of a book with peripheral material, the addition of syllables to a line of poetry for metrical purposes, and so forth. .... expletive is a term in linguistics for a meaningless word filling a syntactic vacancy (syntactic expletives)."
"Syntactic expletives are words that perform a syntactic role but contribute nothing to meaning. Expletive subjects are part of the grammar of many non-pro-drop languages such as English, whose clauses normally require overt provision of subject even when the subject can be pragmatically inferred (for an alternative theory considering expletives like there as a dummy predicate rather than a dummy subject based on the analysis of the copula see Moro 1997 in the list of references cited here)."
In sentences such as
"I forgot to pay the phone bill twice running, so the bloody line was cut off."
bloody contributes nothing to the meaning. Rather, it suggests the strength of feeling (usually anger or irritation, but often admiration, etc.) of the speaker. In having no meaning, it resembles the syntactic expletives discussed above; in these uses, bloody is an expletive. An expletive attributive is a grammatical intensifier.
Other words that are never thought of as offensive can be used in similar ways. For example:
"I forgot to pay the phone bill twice running, so the wretched line was cut off."
The phone line discussed may (before it was cut off) have been just as good as any other, and therefore would not have been wretched in the dictionary senses of "extremely shoddy", "devoid of hope" or similar. Rather, [b]wretched[/b] serves here as a politer equivalent of expletive bloody and the like.