Quite a few writers on usage are at pains to distinguish between fatal and fateful. It all began when H. W. Fowler found a passage in a newspaper using fateful where he felt fatal would have been better. Fowler's OED would have told him that the sense used in the newspaper was first attested in 1764 and the sense he thought fateful was created for was not attested until 1800. Fateful seems actually to have been invented by Alexander Pope earlier in the 18th century for a meaning close to "oracular" or "prophetic." Both Pope's sense and the newspaper's "deadly" sense are uncommon in present-day English.
Fowler also made the pronouncement that fateful could indicate a good outcome as well as an unpleasant one. Almost all subsequent commentators repeat this part of Fowler's treatment. To it, many recent ones add a limitation on fatal. Perhaps the most compendious summary is that of Copperud 1980:
Fatal means death-dealing, fateful productive of great consequences, for either good or evil.
As a description of actual usage, this is something of an oversimplification, and it especially oversimplifies the range of use of fatal.
Fatal is the original adjective for fate. It carries the usual simple relational sense: the Fates are "the fatal sisters." It also has (and has had since Chaucer's time) the sense of "involving momentous consequences, portentous" that the critics prefer to assign to fateful. The usual direction of this portent is toward evil, as Fowler observed:
... if I had been superstitiously inclined to observe days as fatal or fortunate —Daniel Defoe, Robinson Crusoe, 1719
... the constable had orders to take him into custody and lodge him in prison___The news of this effectually frightened him, and he delivered up the 14 negatives ... before the fatal day arrived —Lewis Carroll, letter, 11 Nov. 1886
Then came the fatal letter, the desolating letter — Arnold Bennett, The Old Wives' Tale, 1908
... ever since she had got back to the Vassar club that fatal morning —Mary McCarthy, The Group, 1963
... at Pearl Harbor on the fatal day —David McCullough, Saturday Rev., 27 Nov. 1971
Fateful is used in about the same way:
... the Fuehrer actually made his fateful decision to declare war on the United States on December 9 — William L. Shirer, The Rise and Fall of the Third Reich, 1960
... the Gulf of Tonkin resolution, the fateful declaration adopted by Congress —The Progressive, January 1970
Edwardian England dug the grave into which British colonialism fell in 1945, and the story of that fateful shoveling is told by Mr. Martin —Alden Whitman, Saturday Rev., 6 Nov. 1971
The fateful decision to cover up what we knew to be the true budget numbers —David A. Stockman, Newsweek, 28 Apr. 1986
Fateful does sometimes have at least a neutral, if not quite positive, connotation:
... the day when the fateful letter from the college admission office is due —James B. Conant, Slums and Suburbs, 1961
It is sixty years since Mann undertook that fateful holiday in Venice ... which gave him the basic material for the novella —Times Literary Supp., 30 July 1971
Fatal developed its sense "causing death, destruction, or ruin" in the 16th century. When the meaning is strictly "causing death," it is a sense not shared by fateful:
Although an individual can live with just one kidney, the failure of both is fatal —Neil A. Martin, Dun's, October 1971
... demonstration had been set offby the fatal shooting of ... a prisoner —Paul Jacobs, Center Mag., May 1969
The infection of the fallopian tubes could be fatal — Human Reproduction (9th grade textbook), 1981
Fatal also indicates destruction or ruin, often with the notion of death commingled:
Queen's favours might be fatal gifts, but they were much more fatal to reject than to accept —Henry Adams, Mont-Saint-Michel and Chartres, 1904
He discerns a fatal flaw in the theory —Ronald Gross, N.Y. Times Book Rev., 25 Mar. 1973
... a point of view fatal to any moral force —Kath-erine Anne Porter, The Never-Ending Wrong, 1977
... an error fatal to his entire scientific methodology —Patrick Gardiner, N.Y. Rev. of Books, 20 May 1971
Fateful has been used sporadically in this sense. It is never constructed with to, however, as fatal can be.
He hath loosed the fateful lightning of His terrible, swift sword —Julia Ward Howe, "Battle Hymn of the Republic," 1862
And fatal has a weakened sense that has developed from the "causing death or destruction" sense. The OED suggests that this sense may have come from the human tendency to overstate things, to be hyperbolical.
Being that is a fatal way to begin any sentence — Barzun 1985
Natural logarithms struck the fatal blow. The day the professor broached that subject, my brain sent up a warning signal —Susan McDonald, Hampshire Life, 1 Feb. 1986
Tediousness is the most fatal of all faults —Samuel Johnson, Life of Prior, ca. 1781
For what he wanted as a captain seems to have been ... authority. He should have known that of all wants this is the most fatal —T. B. Macaulay, The History of England, vol. I, 1849
Fateful is not used in this sense. Nor is it used in the sense of fatal that applies to a powerful and dangerous attraction:
... I look forward to becoming a middle-aged sex object of fatal charms —Joan Rivers, McCall's, October 1971
... has a fatal attraction for the stalest figures of speech in the language —Joseph Lelyveld, Saturday Rev., July 1980
... his pursuit of her fatal daughter —Robert M. Adams, N.Y. Times Book Rev., 31 Mar. 1985
Fatal has the wider range of application, and is the more common of the two adjectives.(资料出处：韦伯斯特英语用法词典)