Danny Ruskin.

- Jane's wife, would have been murdered by the Blake association. To extract revenge, Danny kills the members of Blake association or people who helped them one by one… all along he leaves a clue - the smiley in blood, of Jane. This could mean something to both Danny and Jane (viewers might not yet know)

So Red John is someone who is avenging for the same reason as Jane wants to… all along he destroys Jane's old memories - cause he was angry that he took away his sister from him… but at the same time he couldn't bring himself to kill Jane cause he was family.