Try this:
{{ url('/dashboard/medicinepending/', [$val->id]) }}
But it's a bad idea to use relative paths, because if you'll want to change URL scheme, you will need to manually find tens or hundreds links in your views and controllers and change them manually. In this case you'll definitely forget to change some of them and some pages of your app will be broken.
A good practice is to use links to route:
{{ route('name.route', ['id' => $val->id]) }}
Or links to action:
{{ action('MyController@show', $val->id) }}
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