Show the hook attached to a specific filter

show_filters.php

function dc_wp_show_hooked_filters(){
  global $wp_filter;
  $filter_name = 'bp_core_fetch_avatar_no_grav';
  echo '<pre class="filter-dump">';
  var_dump( $wp_filter[$filter_name] );
  echo '</pre>';
}
add_action( 'wp_head', 'dc_wp_show_hooked_filters' );