I think Mitch is expressing anger at a girlfriend or friend ("such beauty" - so probably girlfriend) who has lied to him countlessly in the past - "count the lies on my own fingertips" and how he's thinking about making her pay for her false guidance. He asks for forgiveness for thinking these thoughts.. or if you're really deep into the song then he's asking for forgiveness as he 'murdered' her.
...back to the point.
I think Mitch is expressing anger at a girlfriend or friend ("such beauty" - so probably girlfriend) who has lied to him countlessly in the past - "count the lies on my own fingertips" and how he's thinking about making her pay for her false guidance. He asks for forgiveness for thinking these thoughts.. or if you're really deep into the song then he's asking for forgiveness as he 'murdered' her.