The customary answer is Rameses II, though Fuller asserts the "obvious Ozymandias of Shelley's day" was Napoleon.
This exploration of poetic puzzles ranges from Randall Jarrell's shocking Death of A Ball Turret Gunner ("they washed me out of the turret with a hose") to Wallace Stevens's Emperor of Ice-Cream (Fuller notes, "the national food of a country which has eschewed emperors").
Discussing the poetic force of riddles, he cites a children's rhyme about "a bottomless vessel to put flesh and blood in". Warfare? No, a wedding ring.