He tried to choke my sister.
This isn't the usual "I'm not sure you're telling the truth" drama from my sister, this is confirmed.
Mom and dad are begging me to let them handle it and for me to not do anything.
They are apparently afraid of what will happen when I turn off the light of God within me and let my darkness run rampant. They mentioned they discovered what I was cooking up the last time my BIL nearly hurt my sister several years ago.
I told them they didn't have to worry, what I will do now will be even worse and I'm good enough it will never be pinned on me.
That isn't what they wanted to hear. Considering it's their precious daughter, you'd think it would be EXACTLY what they wanted to hear.
I pegged my BIL for this behavior almost from the day I met him all those years ago. I explicitly stated he had "spousal abuse" written all over him, it was just a question of when. Through his temper tantrums and other behavior, when my parents asked me why I didn't like my BIL, I would tell them exactly why. And I would be told, he's family now and we support family, deep down inside he really loves your sister, it's just his blood sugar from the diabetes, you have a bad temper and you would never hurt anyone and your BIL is probably the same, all that stuff.
To anyone who reads my ramblings, hear this: abuse is abuse. Bad behavior rewarded is bad behavior repeated. It will escalate. It will get worse. Defy this behavior. Stop this behavior. Or leave.
Both for your sake and for the significant other who is looking at a family member ready to go chaotic evil on his ass.