Bears Ears National Monument. The issue was that Obama made that proclamation single-handedly, which is absolutely within his power. But he did it at zero hour (December 28, 2016), and so Trump was able to reverse it in the same manner. There was also talk about reducing Katahdin Woods Monument, also controversial, but that didn’t come about.
Just because dingbats like Lee or LePage are opposed does not automatically make it a bad decision. It’s complicated.
His pick for Interior (Zinke) was not as bad as I expected, supporting e.g. grizzly bear restoration against ranchers and others who theoretically have Trump’s ear.
I don’t know any major people who object to Mattis. And the North Korea thing is still playing out, but might end up good.