This is the 10631st most frequent Russian word.
возглавивший
"Having led" or "who took the lead."
Here, "возглавивший" is used to describe the coach, indicating their role as the person who took leadership of the team.
Возглавивший команду тренер привел ее к победе.
The coach who led the team brought it to victory.
In this sentence, "возглавившем" refers to the individual who took on the responsibility of leading the expedition team.
Эта история о человеке, возглавившем экспедицию.
This story is about the person who led the expedition.
Here, "возглавившего" is used to signify that the new director assumed a leading role in the institute.