It implies a strong sense of moral disapproval and condemnation for an action or behavior.
Here are some synonyms for "reprehensible":
* Condemnable
* Deplorable
* Detestable
* Execrable
* Shameful
* Villainous
* Abhorrent
* Disgraceful
* Unpardonable
Example sentence:
* The company's decision to lay off hundreds of employees while executives received large bonuses was widely seen as reprehensible.