Menachem,
I didn’t have a chance to delve into the specific passage you mentioned from the Tanya, but generally speaking, Chazal teach us that every person, regardless of their stature, contends with a Yetzer Harah. The principle of “כל הגדול מחבירו יצרו גדול ממנו” holds true in this regard. It doesn’t contradict the concept of “ובערת הרע מקרבך”, “צדיקים יצר טוב שופטן”.
However, the central point is that we lack a definitive yardstick to objectively determine whether someone has attained a level (assuming it exists) where they no longer possess a Yetzer Harah.