Who is going to supervise,regulate and operate as lender of last resort with the gigantic banks that are being created? 

首先，with 不可能与前面的三个动词搭配，而且不能共用一个介词。排除作状语。

划线部分（介词短语）作定语，修饰 lender of last resort（最后贷方）。lender of last resort 实指：the central bank of a country with authority for controlling its banking system。

lender of last resort with the gigantic banks， with 表示“持有；拥有；带有” 之意。说明这些大型银行属于国家中央银行的。

that are being created：定语从句（可略去）

lender of last resort with the gigantic banks

直译：拥有这些大型银行的作为最后贷款人的央行。

说白了就是：最后贷款人就是央行，央行拥有这些大型银行。