<?php

$this->builder
      ->select('*') // needs to be here, otherwise the only returned column will be `last_login`
      ->selectSub(function ($q) {
        $q->from('action_logs')
          ->whereColumn('user_id', 'users.id')
          ->selectRaw('max(created_at)');
      }, 'last_login')
      ->get();

// all columns from the table...
// last_login => '2019-01-16 12:34:56'