NEW YORK — The wrap-up of a trilogy of films featuring a vigilante might be taken as an occasion to detail the moral dangers of do-it-yourself justice and to ponder the enduring appeal, in pop culture, of such ethical corner cutting. In the case of “The Equalizer 3” (Sony), however, such an analysis is swiftly rendered moot by the movie’s opening sequence.

In the first of several interludes of hideous mayhem — seen more fully in later flashbacks — Denzel Washington’s Robert McCall, the retired government assassin of the title, not only employs a gun to dispatch his adversaries as he raids a Mafia-run Italian vineyard, he lays one extra low by embedding an ax deep in his forehead. It’s a nauseous foretaste of things to come.

Wounded in the wake of this characteristic killing spree, McCall finds refuge in Altomonte, a picturesque coastal town whose local doctor, Enzo (Remo Girone), treats him without asking indiscreet questions. Staying with Enzo as he recovers, McCall is introduced to Altomonte’s quaint round of daily life, over which Enzo genially presides as one of its leading citizens.

Alas, Altomonte’s civilized tranquility — symbolized, among other things, by repeated images related to Catholic faith and practice, culminating in a saint’s-day procession — is threatened by the surviving colleagues of the mobsters McCall slew back at the winery. They’re led by brothers Vincent (Andrea Scarduzio) and Marco (Andrea Dodero) Quaranta.

In response to this menace, McCall embarks on a two-pronged campaign of crimefighting. While disposing of the siblings and their minions one by one on his own, he first alerts novice CIA agent Emma (Dakota Fanning) to the existence of the international drug smuggling operation they’ve launched and then collaborates with her to put a halt to it.

In their latest big-screen variation on the eponymous CBS-TV series starring Edward Woodward that ran for four seasons beginning in 1985, screenwriter Richard Wenk and director Antoine Fuqua have a few things going for them. Thus they once again profit from Washington’s flair for portraying an understated, quirky killer endowed with an off-kilter brand of charisma.

The duo also successfully evokes almost comic dramatic irony via their villains’ consistent underestimation of the opponent they’re facing and McCall’s subdued predictions of the doom that awaits his hubristic enemies. Yet these mildly intriguing assets are quickly swept away in a deluge of bloodletting as McCall crushes, impales or beheads anyone who gets in his way.

The film contains excessive gruesome violence with much gore, numerous grisly images, brief partial nudity, a narcotics theme, about a half-dozen instances each of rough and crude language and a couple of crass terms. The OSV News classification is O – morally offensive. The Motion Picture Association rating is R – restricted. Under 17 requires accompanying parent or adult guardian.