*ngFor - Loop two arrays in the same level

The ngFor structural directive only accepts a single iterable as input. It won't accept more than one array. Instead of trying to loop through two separate arrays, I would suggest creating a single array (provided both arrays are of the same length).

// HTML

<tbody *ngIf="feedbacks.length">
   <ng-container *ngFor="let item of combinedArray;let i=index">
     <tr>
       <td>{{ i }}</td>
       <td>{{fd}}</td>
         <td colspan="2">
           <ul>
             <div *ngFor="let obj of item.result">
               <td>Test: {{obj.score}}</td>
             </div>
           </ul>
       </td>
    </tr>
  </ng-container>
</tbody>

// Typescript

combinedArray: { feedback: any, results: any }[] = [];

ngOnInit(){
  ...

  this.feedbacks.forEach((fb, index)
    => this.combinedArray.push({ feedback: fb, result: this.results[index] }));
}

try this👇

<tbody>
        <tr *ngFor="let fd of feedbacks;let i=index">
            <td>{{ i }} </td>
            <td>{{fd}} {{results[i].score}}</td>
            <td>{{fd}} {{results[i].tone_id}}</td>
            <td>{{fd}} {{results[i].tone_name}}</td>
        </tr>
</tbody>

use let obj of results[i] for this.

<tbody *ngIf="feedbacks.length">
    <ng-container *ngFor="let fd of feedbacks;let i=index">
        <tr>
            <td>{{ i }}</td>
            <td>{{fd}}</td>
            <td colspan="2">
                <ul>
                    <div *ngFor="let obj of results[i]">
                        <td>Test: {{obj.score}}</td>
                    </div>
                </ul>
            </td>
        </tr>
    </ng-container>
</tbody>