No, not all grubs are bad, in fact grubs are just the larval form of beetles. There are eight times as many beetle species as there are fish, amphibian, reptile, bird and mammal species put together. Whether or not a grub is bad is determined by what it eats.

Stink bugs do not have a larval stage where they look like grubs. They go from egg to nymph to adult so you can rule them out.

Generally if you see a grub here and there they are no cause for concern, it is when you are digging and unearth many grubs that you will want to try and figure out what they are.

So, is there a chance this grub could have turned into a beneficial insect for the garden? I did only see 1 grub in this bed. I have yet to see any in the other 2 beds, or on the other side of the yard that is fruit trees.

Sure, it may have been an eater of decaying material, a beetle that would prey on other insects, a fungus eater, who knows?

Even if it was going to turn out to be a plant eater, a single grub/beetle isn't a big problem.

No big deal, beetles are everywhere for a reason, they know how to survive. Killing an unidentified grub isn't necessary, but it isn't going to wipe the species off the planet any time soon either ;-)

Grubs are the larva of mostly scarab beetles which include Japanese Beetles, June Bugs, Cicadas and many other of those hard shelled beetles. While not all are pests, and all serve as a food source for many other critters, most are. As you dig the wee buggers up put them out as an offering for your birds.