“However, every time that Marxism(communism) has been implemented on a nation wide scale it has been an unmitigated disaster.”

Marxism isn’t any kind of system to implement. Communism, on the other hand, is and, contrary to your first claim, has never been implemented anywhere, thus disproving your second claim that communism has been a disaster every time it has been implemented.

“When all products are to be shared, it takes away the incentive to work hard in order to succeed.”

This is an unfortunately common misconception, that all products under socialism and/or communism are shared. What it comes down to, for those experiencing this misconception, is the erroneous conflation of private property and personal property. So to wipe your misconception, this is the difference: The former consists of anything that is used to generate profit, like the means of production, while the latter consists of anything with mere use to its owner, like one’s car, house, and toothbrush. All socialists, including communists, want to abolish only the former, not the latter. This means that even if the quote above were true, it wouldn’t, and doesn’t, apply to socialism or communism because neither entails the sharing of all products.

“Here is a partial list of large scale communist states that failed dramatically. Russia(and most of Eastern Europe), Vietnam, Cuba, Venezuela, North Korea etc...”

No country anywhere, including these, was ever systemically communist but rather, at most, ideollogically communist, dictatorships of the proletariat, and/or systemically socialist.

“I know that many people are very passionate about Marxism one way or the other, but the death toll caused in its name over the past century is truly staggering and terrible.”

Okay, let’s assume you’re right, that “Marxism” has indeed caused a “truly staggering and terrible” death toll. Now let's compare it with capitalism's:

Why defend capitalism when its death toll is far worse? Every year, millions of people die from preventable causes—lack of water, food, vaccines—all because capitalism is organized to generate profit as opposed to satisfy needs. Communists, on the other hand, proclaim, “From each according to his ability, to each according to his needs!”

You're in dire need of education. Fortunately, because you sound more or less open-minded, I’ve made a reading list below for you to educate yourself, which I highly recommend you do not pass up. (What I did above wasn’t a rant, by the way, but merely a correction of substantial misinformation.)

Socialism 101 is a site that you should visit asap; it scratches the surface of socialism, designed only to get you started, http://socialism101.com/basic/.

The Draft of a Communist Confession of Faith (1847) by Frederick Engels is a really short work and is a precursor to the Principles of Communism (1847) by the same author, https://www.marxists.org/archive/marx/works/1847/06/09.htm.

The Principles Of Communism (1847) by Frederick Engels is a short work in the form of a Q and A like the Draft of a Communist Confession of Faith (1847), https://www.marxists.org/archive/marx/works/1847/11/prin-com.htm.

Behind Soviet Power: Stalin and the Russians (1946) by Jerome Davis, an American sociologist who’s been to Russa multiple times and has conducted numerous interviews in Russian, is a good book about Russa back then, https://babel.hathitrust.org/cgi/pt?id=mdp.39015014821030;view=1up;seq=1.

Wage Labor and Capital (1847) by Karl Marx is a short, well-written work on economics, which should give you an idea of what Marx talked about in the field of economics, https://www.marxists.org/archive/marx/works/download/Marx_Wage_Labour_and_Capital.pdf.