* Unbreakable: Not able to be broken.
* Unforgivable: Not able to be forgiven.
* Inexcusable: Not able to be excused.
* Inoperable: Not able to be operated on.
* Indelible: Not able to be erased or removed.
* Inaccessible: Not able to be reached or entered.
* Irreparable: Not able to be repaired.
* Unreadable: Not able to be read.
* Incomprehensible: Not able to be understood.
* Unbearable: Not able to be endured.
* Unthinkable: Not able to be imagined or considered.
Note: Many of these words are formed by adding "un-" to a positive word.