独步一时: be unequaled in one's generation; be unparalleled for a time; reign supreme in one's own field for some time; set the pace for the generation; stand alone in..
天下独步: be unparalleled [unequalled; unmatched] in the world [under heaven]; cut a great figure; dominant
独步天下: there is none under heaven to equal him.; be unparalleled [unequalled; unmatched] in the world [under heaven]; cut a great figure; dominant; there is none to equal him on (the) earth
独步古今: have no equal in both ancient and modern times
月下独步: take a solitary walk in the moonlight; walk alone under the moon; walk by alone moonlight