unjustifiable

un|jus|ti|fi|able /'ʌndʒʌstɪf'aɪəb^əl, ʌndʒ'ʌstɪfaɪəb^əl/
[ADJ]
If you describe an action, especially one that harms someone, as unjustifiable, you mean there is no good reason for it.
Using these missiles to down civilian aircraft is simply immoral and totally unjustifiable.
≠ justifiable
● unjustifiably [ADV]
The press invade people's privacy unfairly and unjustifiably every day.
≠ justifiably