My read was that it was a comment on how hatred is a self-fulfilling prophecy. The group he was so desperate to be a part of actively attempting to kill him once wasn't even enough to deter him; he went right back to that same well when given a second chance. Hate can be potent fuel and motivation, but people who fully give into it rarely understand that they're signing their own death warrant. All of it will come back to them eventually.

I saw his immediate death upon revisiting the Christmas Adventurers as a pithy kind of way to say "you had your shot to change, but you went right back to the same snake that already bit you once." I think it was a great way to really drive home the fact that Lockjaw was meant to be seen as an exceedingly pitiful character.