Synonyms for Top dog:

n.

high-flier, survivor, hotshot, boy wonder, success story, performer, superwoman, leader. big deal (noun)
hotshot.
boss (noun)
leader, chief, head.
top dog (noun)
chief, head.

Other synonyms:

success story, hotshot, survivor, superwoman, boy wonder, performer, high-flier. leader. Other relevant words:
leader.