This is the 18158th most frequent Russian word.
целеустремленностью
Single-mindedness or determination.
In this sentence, 'целеустремлённостью' refers to someone's strong and admirable character trait of being focused and determined towards achieving their goals.
Её целеустремлённостью можно только восхищаться.
You can only admire her determination.
Here, 'целеустремлённостью' emphasizes the quality of persistently striving towards a goal as the key factor for success.
Целеустремлённостью он добился успеха на работе.
He achieved success at work through determination.
In this case, 'целеустремлённость' highlights the personal attribute of strong will as an inspiring factor to others.