I tried Nidhogg (or the last boss on Nidhogg since Nidhogg seems to be the giant hell centipede). But all my teams died on his second form. I don't even know how many forms it has. Golds are just not done for this job.
But, now I can clear (but not complete) 4th step maps with thoses broken slice pests. Farming Roses medals will be a bit easier.