As has been said, Biden is a decent guy and in no way comparable to Trump in terms of his ethics, except on this issue where he did what he always said he wouldn't do.
No doubt the Republicans went after Hunter Biden hoping to get to Joe, and he certainly had drug issues which got him into trouble, but at the end of the day Joe stayed above it and Hunter pleaded guilty as charged. That should have been the end of it.
If he wasn't the president's son, and the president had not caved at the end of the day, he wouldn't have got this pardon, and that's the problem.
Trump of course would be happy to pre-emptively pardon Don Jr just in case he ever committed any crimes. Half of Trump's cabinet picks have criminal records, including Trump himself, so by comparison Joe is a comparative saint despite this late embarrassing backflip.