I have nothing against him personally, I just don't think he's the right man for the job.

have 是动词，表示"拥有"或"持有"的意思。 nothing 是代词，表示"没有任何东西"或"零"。 against 是介词，表示"反对"或"与...对立"的意思。 have nothing against 是一个固定短语，意思是"对...没有反对意见"或"对...没有成见"。