TW - How are we dealing w/ extremely violent toddlers?

TW Violence

I'm not looking for parents of "big feelings" kids. I mean the parents who have been and are constantly attacked by their toddlers during meltdowns and tantrums. I'm talking biting till bruising or blood, scratching at eyes and punching and kicking in teeth. I restrain as best as possible so she cannot hurt me, herself or her 11mo sibling but she will either headbutt or bite where ever she can HARD. Im genuinely worried that she will take a chunk off my ear lobe.

I've tried the talk it out approach, I've tried the hug it out. I've tried alone time. I've even resorted, shamefully, to "90s parenting methods" (if possible, refrain from the lectures on this. I know it doesn't work.)

She is an absolute sweetheart all the time. Typical 2.5yo level of defiance, but meltdowns and tantrums.. its like a whole different child comes forth and I genuinely do not recognize her. They are only ever this bad when her dad is home but he is never the victim, only the savior. Its wearing me out physically, mentally and emotionally. To save the sob story, I just feel like she tolerates me when he's gone, but when hes home shes safe to show how much she hates me.

I just dont know what I'm doing wrong. Yes, postpartum with my second hit hard. I will admit I was very quick to temper those first few weeks. Did that really fuck everything up? I'm at a loss and can't figure out where I went wrong that she doesnt feel safe to even get a diaper change from me, it has to be her dad. She wont sleep near me, has to be her dad.

How can I fix this? How do I regulate my toddler?