[SPOILER] Everybody in the HQ are dead??

I believe Raikage's assistant and quite a few other ninja's

HQ was in Kumo, Kumogakure was nearly wiped off the face of the planet. Quite a few people died. But if you mean named characters then Inoichi, Shikaku, Mabui the Raikage's assistant and Ao the Kiri ninja with the Byakugan implant.