For me, since I usually just beat the main story as quickly as possible, any chapter that I can't do with just Chrom, MyUnit, and Frederick is annoying. Particularly Chapter 6 and the one where you have to defend Tiki. --- On a side note, it's always really fun to save Aversa's recruitment chapter until you're Apotheosis ready and then challenge it with all your capped units with their optimal skillsets.