Respectful Noun for Really Hard Worker

Someone who is more than just a hard worker can be described as persevering:

To persist in or remain constant to a purpose, idea, or task in the face of obstacles or discouragement. The three great essentials to achieve anything worthwhile are, first, hard work; second, stick-to-itiveness; third, common sense. ― Thomas A. Edison I do not think that there is any other quality so essential to success of any kind as the quality of perseverance. It overcomes almost everything, even nature. - John D. Rockefeller

passionate:

having, compelled by, or ruled by intense emotion or strong feeling; fervid; zealous. I have no special talents. I am passionately curious. -Albert Einstein (1879 - 1955) When natural inclination develops into a passionate desire, one advances towards his goal in seven-league boots. - Nikola Tesla I think I overcame every single one of my personal shortcomings by the sheer passion I brought to my work. I don’t know if you’re born with this kind of passion, or if you can learn it. But I do know you need it. - Sam Walton

disciplined:

Controlled behavior resulting from disciplinary training; self-control. Does thou love life? Then do not squander time; for that’s the stuff life is made of. - Ben Franklin Things may come to those who wait, but only the things left by those who hustle. - Abraham Lincoln (1809-1865) In reading the lives of great men, I found that the first victory they won was over themselves… self-discipline with all of them came first. - Harry S. Truman (1884-1972)

dedicated:

Wholly committed to a particular course of thought or action; devoted. It is rather for us here dedicated to the great task remaining before us, that from these honored dead we take increased devotion to that cause for which they gave the last full measure of devotion. - Abraham Lincoln (1809-1865)

zealous:

Filled with or motivated by zeal; fervent. Allowing only ordinary ability and opportunity, we may explain success mainly by one word and that word is WORK! WORK!! WORK!!! WORK!!!! - Frederick Douglass (1818-1895)

ardent: Displaying or characterized by strong enthusiasm or devotion; fervent.

syn: perseverance, persistence, tenacity imply determined continuance in a state or in a course of action. perseverance suggests effort maintained in spite of difficulties or long-continued application; it is used in a favorable sense: The scientist's perseverance finally paid off in a coveted prize. persistence, which may be used in a favorable or unfavorable sense, implies steadfast, unremitting continuance in spite of opposition or protest: an annoying persistence in a belief. tenacity is a dogged and determined holding on: the stubborn tenacity of a salesman. (TFD)

Perhaps diligent:

diligent

1. constant in effort to accomplish something; attentive and persistent in doing anything.
2. done or pursued with persevering attention; painstaking.

Dictionary.com

Edit: In light of the updated question, some more options include achiever:

achiever (one who achieves), i.e.

1. to bring to a successful end; carry through; accomplish
2. to get or attain by effort; gain; obtain

Dictionary.com

Or man of action:

man of action:

1. A person who prefers to act rather than contemplate and gets things accomplished quickly an efficiently.

TheFreeDictionary.com

The latter does have connotations of the "shoot first, ask questions later" type, however.

'Nother edit: thanks to medica's suggestion, I found a definition for high achiever:

high achiever:

1. a person who achieves more than the average person in their work

Cambridge Business English Dictionary - Cambridge Dictionaries Online

A trooper would fit. A trooper is a soldier, but the term is often used colloquially to mean someone who works hard, or is persevering.

Jane is a real trooper she stayed in all weekend to get the report done by monday.

Also a team-player. A team-player is someone who works for the good of the team.

Jim is a great team-player, he changed his lunch plans so he could help out at a critical meeting we had.

You asked for a noun but oddly, most of the answers above seem to be adjectives. May I suggest a stalwart. This is positive, despite appearances, and seems to have pretty universally gone from meaning strong, courageous, and persevering to meaning someone who is the backbone of some operation.