Again, the rules are made up, but there are a dozen listed sins that are unforgivable. You just have to look for them.
However, a deal with the devil is automatically considered blasphemy against God, and thus an unforgivable sin. Add in the sin of Pride, and Johnny is damned.
Christianity’s whole thing is that no sin is unforgivable (except deliberate rejection of the Holy Spirit’s work/testimony about Jesus (Mark 3:20-28))
Again, the rules are made up, but there are a dozen listed sins that are unforgivable. You just have to look for them.
However, a deal with the devil is automatically considered blasphemy against God, and thus an unforgivable sin. Add in the sin of Pride, and Johnny is damned.