css z-index issue with nested elements

Don’t specify any z-index to .bank to avoid creating new stacking context and simply adjust the z-index of the other elements. This will work because all the 3 elements belong to the same stacking context so you can specify any order you want.

.bank {
  position:relative;
  background: red;
  width: 500px;
  height: 200px;
}

.card {
  position: absolute;
  top:0;
  z-index: 2;
  height: 100px;
  width: 400px;
  background: blue;
}

.button {
  position: absolute;
  top: 0;
  z-index: 1;
  height: 150px;
  width: 450px;
  background: yellow;
}

.container {
  position: relative;
}

<div class="container">
  <div class="bank">
    <div class="card"></div>
  </div>

  <div class="button"></div>
</div>

UPDATE

Considering you code, the only way is to remove the z-index and transform from .bank or it will be impossible because your elements will never belong to the same stacking context. As you can read in the previous link:

Each stacking context is self-contained: after the element’s contents
are stacked, the whole element is considered in the stacking order of
the parent stacking context.

Related for more details: Why can’t an element with a z-index value cover its child?