A relative clause is not grand simply because it is long. Magnification arises from the weight of the attribute or achievement it brings to attention, not from word count.
«الذي فتح باب الغرفة جاء» — The person who opened the room door came: ordinary identification.
«الذي نصر المظلومين وقت الخوف جاء» — The person who defended the oppressed in fear came: the clause suggests praise and stature.
Both are grammatical relative constructions. Their differing rhetorical force comes from the value and relevance of the information in the clause.