No grounding bar

Is this grounding screw okay or should there be a grounding bar there is another wire nutted to the larger wire as well? These are the only NM wires everything else is in conduit. It’s in a sub panel.

That is a standard 10-32 ground screw. The issue is whether it has two threads in contact with the box.

Thanks Jim, there were a couple of things wrong so I can work with that. Thanks again.

The connection to the enclosure must be sized by the largest EGC contained within the splice in the panel. Looks like there are large conductors within that visible splice in the photo.