先せん鋒ぽう

先せん陣じん
先陣 keeps a strong military connotation and appears fixed in 先陣を切る, while 先鋒 is more common in sports and competitive contexts for the leading member of a group.
一いち番ばん手て
先鋒 is a somewhat literary term for the one who takes the initiative or leads an attack, while 一番手 is a more neutral, everyday word for the first person to act.
先さき駆がけ
先鋒 names the frontmost fighter or spearhead of a group action, close to 先駆け's second sense of leading an attack.

Opposites

大たい将しょう
In team martial arts, 先鋒 is the first competitor to fight while 大将 is the last, usually the team's strongest member.
殿しんがりN1
先鋒 is the vanguard or lead unit in an advance, the military opposite of 殿（しんがり）, the rear guard.

Word family

急きゅう先せん鋒ぽう
vanguard; forefront; leading figure

Etymology

A Sino-Japanese word inherited from Chinese 先鋒, combining 先, “foremost,” and 鋒, “weapon point” or “spearhead.” It originally denoted the foremost attacking force and later the first competitor in a team match.