if you have to deal with an overblown, toxic 'critic' voice in your head then you certainly deserve a warm, positive voice too...
...and to listen to it.
If it were a match between the two, what is the score? Which of them is louder? Is it even a fair match?
'cuz a healthier baseline doesn't looks like a trounce. Recognizing this isn't necessarily a bad thing, though, because that sort of information helps when it comes to the work of deescalating said 'critic' voice.
Every time I recognize that voice talking in my inner thought process, I ask myself what the score is.
I know it's hard to even get there, because sometimes that voice sounds or even is right sometimes. I propose that it doesn't matter how Right that voice sounds in the moment. It can't matter both because that way furthers the toxic cycle and does not break it (and that's the level you sometimes have to think) and because it isn't fair to you. How is the match going? is it relentless? is that self-care?
For what it's worth, the world is hard enough. You are worthy of having that positive voice in you eventually start winning.

(I say 'critic', 'cuz i'm not fond of the "angel and devil on your shoulder" metaphor. It's still a similar concept to what i'm referring to)