Im thinking Teddy carried on the tradition of beating benny since he was seen as the best. He eventually went overboard and maybe tried to bleach him to be seen as "better" and fukked up benny.
Maybe Benny was against it Teddy hurt him and thought he killed him and stashed him in the basement.
After that he focused on himself.
Then maybe Teddy thought the biggest sacrifice he could make, to make himself great, was to take a life.
OR
Benny and Teddy were the dad's sacrifices. So Teddy made Benny his sacrifice. And after he thought benny was dead he wanted to kidnap darius but after seeing that darius was non chalant and didnt play, the best thing would be to take his life