It's takes a lot of work and mindfulness to shrink it I guess. You can refer to Pete's book on the 14 most common critic attacks in Chapter 9: Shrinking The inner Critic.

For me perfectionism is my biggest problem, because I always polarize to all-or-non thinking. It's very difficult to let go of it.

I just took this quote from Pete's book

"The work of shrinking the critic is one of the most essential processes of recovery. As obvious as its value may seem as you read this, embracing the task of renouncing the critic is much more challenging than it may seem at first blush. The critic’s programs are not only burned deeply into our psyches by our parents, but we also unknowingly emblazon them into our minds by mimicking our parents. We are now the key reinforcing agents of their toxic legacy. With little mindfulness of it, we injure ourselves with countless angry, self-disgusted repetitions of their judgments. Recovery now depends on you withdrawing your blind allegiance to this terrible process of only noticing yourself negatively."

I'm not sure how to answer your question of is the inner critic always something negative... I'm trying to correlate thoughts that affect my mood negatively with critical inner attacks... like if I say to myself I'm stupid... then this thought will make me depressed, worthless, etc, then I must be mindful about saying to myself I'm stupid.

Hope this helps