hired gun

broadly idiomatic

A person who is employed as an armed guard, enforcer, or mercenary and who is prepared to use gunplay or similar violent methods in order to assert the interests of his or her employer.

Japanese Meaning

雇われた武装警備員、暗殺者、もしくは傭兵として、雇い主の利益を守るために暴力行為（銃撃など）を行う者。

What is this buttons?

After the deal went sour, the corporation brought in a hired gun to intimidate the smaller company.

Google Translation / DeepL Translation

取引がこじれた後、企業は小さな会社を威圧するために銃を持った傭兵を雇った。

Details

Sense（1）

A person who is employed as an armed guard, enforcer, or mercenary and who is prepared to use gunplay or similar violent methods in order to assert the interests of his or her employer.

Details

Sense（2）

(idiomatic, by extension) A person who is employed to advance the interests of his or her employer, especially in a vigorous manner using such methods as political lobbying, legal advocacy, or persuasion.