barbaric / barbarous / barbarian
Cruel or crude, savagely cruel, and the person.
Barbaric means crude or cruel, sometimes with a note of raw vigor. Barbarous is harsher: savagely cruel or uncivilized. A barbarian is the person. The words overlap. If you mean only “very cruel,” barbarous is the sharper word. If you mean “rough, unrefined,” barbaric will do.
Examples
Usea barbaric yawp
Usea barbarous punishment
UseThe barbarian army crossed the river.
Avoida barbarian punishment (If you mean the act was cruel, not that a barbarian performed it.)