Demogorgons have been repelled by a reasonably athletic teenager with a baseball bat. It is immune to small-arms fire, but only like, submachine guns. The exterior of the Quiet Place monsters is impregnable to all conventional weaponry used on them and some outlier feats place them above that, like surviving their world exploding and then the impact of their meteor hitting the ground.
They can also tear through the solid metal siding of a silo as seen here:
Demo gets ripped to pieces.