It's funny, in researching Maxwell I wanted to make note of his less than stellar courses. I would say the three that I found the least inspiring that I've seen that were still in somewhat the shape he left them in were the following.
Lawton CC in Lawton, OK. This was a routing that he did in one afternoon. The lack of time on site shows. The routing really does make the best of what was there, but there just isn't much there. The work by Tripp Davis to add a second nine and grass the greens helped a little, but the maintenance on the fairways was really not bringing out the few aspects of the design that were there.
Princeton CC in Princeton, KY. This course is of note because of it being where Maxwell lived for his youth. The routing was done while working in Michigan at Crystal Downs and U of M and again, I think that was the only time Maxwell saw the site. The construction was handled by either Dean Woods or Par Woods (I think Par) and no bunkers were used on it originally. Subsequent work by Jerry Lemons added 9 holes and regrassed the original holes. A couple of holes like the 11th and the 16th have some nice land to work with, but overall a 2 on the Doak Scale.
Blackwell GC in Blackwell, OK. Just a totally flat site with only a creek providing any natural interest. The sand green design was used it as best it could, but again, just not much there.
The one notable design by Maxwell that I would say could be somewhat a downer would be Hillcrest in Bartlesville, Oklahoma. It has some great holes, but then it has some really just plain holes. Aside from his premier designs many of these have had a lot of work done to them over time though, so its hard to tell if that is a by-product of him or the people that followed.
There were perhaps some others in the early days of Oklahoma but they have been totally remodeled so I don't know if the quality of the work was from Maxwell or from whomever worked on them since.