Can bad people go to heaven and ruin it? Reconciled by regeneration: everyone who believes in Christ receives a new nature. Even hypothetically, if Hitler truly repented on his deathbed, he'd be a new creation in heaven — hating his old ways, transformed by the Holy Spirit. Heaven is populated by transformed people, not merely forgiven ones.

The reconciliation: everyone in Christ is a new creation (2 Cor 5:17). Heaven won't be "ruined" because every occupant is transformed — the flesh is gone, glorified bodies received, Holy Spirit fully connected. Without Jesus, everyone is bad and would ruin heaven. With Jesus, transformation is complete. The final transformation comes with glorified bodies — the flesh is removed entirely.