Show all post titles

Have not tested it but this should get you to your goal. I believe Accore LTD has it correct as well, except your slide #s will be post ID, instead of slide-1, slide-2

<div class="content">
  <?php if ( have_posts() ) : ?>
  <h2><?php single_cat_title('',true); ?></h2>
 <div>
   <ul>
     <?php 
     $inc = 1;
     while ( have_posts() ) : the_post(); ?>
     <li data-slide="<?php echo $inc; ?>"><?php the_title(); ?></li>
     $inc++;
     <?php endwhile; ?>
     <?php else : ?>
     <?php endif; ?>
    </ul>
  </div>