I actually think some of his paintings and sketches look quite good for a young artist, who hadn't even received proper training yet. There are some more available on Wikimedia Commons:
https://commons.wikimedia.org/wiki/Category:Paintings_by_Ado...
https://commons.wikimedia.org/wiki/Category:Paintings_by_Ado...
This one makes me think that it would be an amazing trolling opportunity to remove the signature, create high-quality reproductions of this “Mary with Jesus” and give them out to American Evangelicals, as the art style generally matches the Christian fundamentalist taste: https://commons.m.wikimedia.org/wiki/File:HitlerMaryWithJesu...