Chapter 3 is already hard to no hit alone due to some annoying encounters like Weather Duo, Shuttah, Rouxls, Tenna and Knight and in all recruits you also have to recruit 3 pippins encounter and especially water cooler which is a pretty bad encounter.

Chapter 4 is not as hard as chapter 3 no hit but there are some annoying parts like chase 1 for example where Knight spams the blades very quickly and much more.

Chapter 1 is not so bad to no hit and if you are looking for a deltarune no hit, you can start with that :)