determinedI was determined not to give up.
doggedHer dogged determination to uncover the truth about the scandal led to her winning a reporting prize.
persistentThe shop never gives refunds, but if you are persistent, they may.
resoluteformalWe must remain resolute in the face of opposition.
single-mindedShe was single-minded and uncompromising in her work.
tenaciousHe is tenacious in fighting for causes he believes in.
pertinaciousformalThe couple’s pertinacious demands to have the law changed for their benefit were a constant source of aggravation for the council.
perseveringShe was described as a persevering woman with great willpower.
perseverantformal,old-fashionedScientists are very perseverant people.