Single word for the one who completes his tasks at any cost

My research shows possible term for the one who completes his tasks at any cost.

  1. Stubborn - Adjective -

The Cambridge Dictionary: a stubborn person is determined to do what he or she wants and refuses to do anything else.

Additionally, the Urban Dictionary (UD) a stubborn person always thinks he's right. These words made me confuse to select this term or not for the one who, whether or rain or shine, completes his tasks.

I don't mean that the term must refer to the who thinks he is right all the time. But, I need that term, that refer to the person completing his tasks such as homework, duty, etc, and is not rude to others.

Is it okay to regard this type of person as determined or tenacious?


Is it okay to regard this type of person as determined or tenacious?

Certainly. I also like:

tenacious TFD

Extremely persistent in adhering to or doing something; stubborn or relentless


Diligent or obsessed may work for your purposes. Both connote a task oriented person, one perhaps more intense (and still positive) than the other. It depends on context used of course.