Eloquente molti-a-molti-a-molti - come caricare facilmente una relazione distante

Ecco come puoi farlo:

User::where('id', $id)->with(['groups.permissions' => function ($q) use (&$permissions) {
     $permissions = $q->get()->unique();
}])->first();

// then
$permissions; // collection of unique permissions of the user with id = $id