strictly speaking for just singles, my top "hatest" song per group:
Morning Musume:
Ambitious (OG era) - my forever oshi is 07 but this song rubs me the wrong way, i dont know why.
Sukatto (Current era) - probably this is the first song that stirred away from the usual EDM sound that they had.
Berryz Koubou - Be Genki - everything about this song is just weird even for berryz, from the arrangement to the costumes.
C-ute - SHOCK - i love Airi to bits, but this song was just unfair to the other members.
ANGERME:
Koi ni Booing Buu (S/mileage era) - they went over the top here.
Kagiriaru (ANGERME era) - this just bores me to death.
Juice=Juice - Next is you - i know they're portraiting a fictional group here, and it did somehow show that its not very ju=ju.
Country Girls - Peanut Butter - the monologue in the beginning threw me off and it affected the whole song for me.
Kobushi Factory - Start Line - probably i just dont like most "rock-ish" H!P songs.
Tsubaki Factory - Shuukatsu - just why? they took the song literally with their office lady dresses. hahahahahha. it made the PV boring.
BEYOOOOONDS - Now Now - i know beyo is like half troupe group, but their dialogue bit is getting over used -- probably like how other's hate the growl in Kobushi.
Random Songs:
Renai Sentai (Nochiura) - great set of soloists, super bad song
Aoi Sports Car (Aoiro7) - worst shuffle song for me at least