盟主|めいしゅmeishu[1]atamadaka (head-high)

1. nounleader (of an alliance); leading power

• RelatedリーダーNeutralLoanword for a leader or captain; the most broadly used of these words, but it doesn't stress an alliance relationship the way 「盟主」 does.
• Related主導者しゅどうしゃWrittenA person who directs others and pushes things forward at the head of a group; stresses spearheading progress, and is written/formal prose.
• Related巨頭きょとうNeutralA magnate or big name with major influence in a field, as in 「財界の巨頭」; stresses influence rather than heading an alliance.

Use 「盟主」 for the country, organization, or person that dominates an alliance, as in 「業界の盟主」 or 「同盟の盟主」. For leadership in general say 「リーダー」, for influential magnates 「巨頭」, and for someone driving things forward 「主導者」.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

1. 同盟どうめいの主宰しゅさいとなる者もの。