Actually you can limit your options:

$('selector').select2({
  maximumSelectionLength: 1
});

You are not the first person to try to do this. But it is not available now.

You can check this issue for some variants: https://github.com/ivaynberg/select2/issues/1345

The developers answer for this issue was:

This has been pulled in for the 4.1.0 release (forgot to tag it), so with any luck this should hit the Select2 core or be available as a plugin within the next few months.

Now it has version 4.0.3, wait for new release and hope that they realy do this :)

I am not sure whether you asked for this. But i was searching for this and though being late, thought it will be helpful to someone.

I have used SCSS.

Demo Here: https://jsfiddle.net/ufr4dw5j/

  .js-example-basic-single{
    width:200px;
  }  
    .select2{

                  &.select2-container{
                      top: -4px;
                      .select2-selection--single{
                          height: 50px;
                          border-radius:0;
                          &:focus{
                              outline: none;
                          }
                          .select2-selection__rendered{
                              line-height: 50px;
                          }
                          .select2-selection__arrow{
                              display:none;
                          }

                      }


                  }


              }

              .select2-container--default{
      &.select2-container--open{
          top:6px !important;
      }
      .select2-dropdown--below{
          top: -4px;
      }

      .select2-search--dropdown{
          padding: 0;
          .select2-search__field{
              height: 48px;
              border:0;
              border-bottom: 1px solid #aaa;
              padding:10px;
              box-sizing: border-box;

          }
      } 
  }