"成为最有发言权的人'用英文怎么说

To be the man who has the final word.
请看马丁路德金名言：
“我没有武装的真理与没有条件的爱在现实生活中是最有发言权的”（小马丁·路德·金）。
“I believe that unarmed truth and unconditional love will have the final word in reality” (Martin Luther King, Jr.).

若仅表示有发言权，可以是
To be the speaking role.

Human who becomes most has the right to speak

或者Become the most people have a say

To be the man who have the final word in something.