majority

aggregate, amount, entirety, quantum, sum, sum total, total, totality, whole

bottom, essence, essentiality, marrow, meat, nature, pith, quintessence, root, soul, stuff, substance

center, heart, hub, kernel, middle, nucleus, nut, seat

affair, argument, burden, crux, focus, gist, nub, pitch, point, purport

matter, motif, subject, text, theme, topic

directress, mistress

administrator, commander, director, executive, general, governor, hierarch, higher-up

leadman, manager, overseer, principal, skipper, standard-bearer, steward, straw boss, superintendent, superior, supervisor

dominator, lord, overlord, potentate, ruler, sovereign (also sovran)

figurehead

slave driver

baron, czar (also tsar), king, magnate, mogul, president, prince

big cheese, big gun, bigwig, top dog, top gun

cohead, coleader

employer, gaffer [British], ganger [British]

micromanager

subchief, subdirector