Ciel was easy for me, since I had EV-trained Mamoswine with Ice Shard. Luna was easy because of Close Combat on Infernape (yeah I went for the easy version). I don't remember why shade was easy, but he was. The first poison gym leader was easy because Swoobat simple-calmminded up and swept.
Other than those, they were all really difficult. I had expected to have an easy time against florinia given almost my entire team had the type advantage, but that didn't happen.
The hardest one was Charlotte, I think. I ended up having to train a staraptor and a rhyperior from scratch, and even then had to figure out the AI's strategy through losing >10 times before I could manipulate it to let me have a chance.