Derek is responsible for the deaths of his entire family.
He’s responsible for Erica’s death.
And now Deucalion wants him to kill his pack?
That’s why he threw the glass at Isaac. Because he needs Isaac to hate him. He needs him to leave him; go to Scott. Find a new Alpha.
He needs his Betas to leave him and he’ll do whatever it takes.
Because he can’t be responsible for more of his pack dying.