Kind of the opposite to "Say something nice about your favourite character". I thought it would be fun to do something like this. I'll start.
Hana's English voice is annoying.
The same goes for Mia and Olivia.
Nowi's outfit makes no sense.
Nyx is a shitty unit.
Ophelia is basically Owain with boobs.
Chrom can be pretty bland.
Lissa isn't a good combat unit.
Frederick can fall behind if you don't use him regularly.
Story-favouritism for Alm is pretty annoying.
I hate Genny's ending.
I also dislike how Celica is reduced to damsel in distress in Act 5.
Saber's haircut looks goofy.
Palla, Catria and Est don't live up to the hype surrounding them in Echoes.