I see a lot fingers at Obito, honestly he felt truly alone and that the world was only full of hatred and death so he declared it as hell. I'm sure I could concur with Obito if I saw my girlfriend/crush killed in front on me. Still the fact at hand is it's not his fault, not fully anyway. Kaguya may have created BZ to do sneaky stuff to make sure she's revived, but it's not it's fault either. It's Hagaromo's for not seeing through his mother and catching her creation before it got out of hand. It's greatly unknown why she continued to give the world grief, but she shares responsibility with her two sons. If it weren't for Kaguya, BZ would've never been made; If it weren't for Hagaromo's inaction, BZ could be gone and his sons would've probably got along a bit better. Overall, the blame can't be placed on any one person but a number of people, because they all had the choice to do different actions yet they all choose the latter. Since Kaguya isn't on the poll I choose Hagaromo.