The Ya’avetz (Mor U’Ketzia, Orach Chaim 225) notes that while Chazal instituted a blessing for seeing a dwarf: “Blessed are You... Who makes creatures different”, they did not specify what blessing to say upon seeing a giant. He explains that such people are exceedingly rare, “perhaps one in a generation.”
In practice he rules that if the person’s stature creates an impressive and beautiful appearance, one should recite the blessing: “Blessed are You... Who has such creations in His world”, the same blessing said upon seeing someone of exceptional beauty. However, if the height is deforming and creates disproportion, no blessing is recited.
He recounts that as a child in Amsterdam, he once saw the emissary from the Holy Land, Chacham Yitzhaki, who was exceedingly tall, handsome, and dignified: “a head and shoulders above all.”
