Jacob

"If you shoot me, it won't reinstate you into the pack. If you could possibly win one-on-one against me, then maybe they'd vote you back to lupa. But if you just shoot me, you'll never be lupa again."
"I'm going to say this nice and slow, Jacob, so we understand each other. I don't give a shit about being lupa. I care about my friends and the people I've promised to protect. Gregory is one of those people. If he dies, you die."

(Narcissus in Chains, page 147, paragraph 4)

* Because of him, Anita has to "petition" for Gregory's life. So Anita promises to kill Jacob, unless he doesn't try to go after Richard's job and unless he helps her solve the problem with Gregory.

* There is a ruthless quality about Jacob that Anita cannot see in Richard.

* When Richard and Sylvie both acknowledge that until the ceremony, Anita is still lupa, she kicks Jacob in the nose and breaks it.

* It was Jacob's idea to put Gregory in the oubliette. So when Gregory was rescued, Anita had Jacob put down there in his place. He was put in silver chains, but he wasn't subjected to the same torture as Gregory.

* It's revealed that Jacob, Paris, and some other unnamed wolves in Richard's pack were actually part of another pack, Zeke's. They were placed in Richard's pack so that Jacob could rise through the ranks and eventually become Ulfric so that he could give the pack over to Chimera.

* When Anita is made Bolverk, she executes Jacob.