Depends ...
Are we talking about BG-3, or tabletop?
And if BG-3 is the case, who is figting the Barbarian, what they have at their disposal, and same question goes to Barbarian.
Fun fact:
In tabletop its not so easy to wait when Barbarian ends his rage, bcs (unless your DM is especialy pedant) there is littealy no rule against attacking ... yourself!
So Barbarian without target in meele range can easily prolong his rage by beating his own chest as unarmed attack ... with resistance, the damage is minimal.
And if you want to make it even funnier, remember that there is not specified even what exactly is unarmed attack ... so you can claim you headbuted your shield instead.
