It's not easy; if you gather to defeat the Barbarians, you need to try hard! It's quite difficult to defeat them due to their good defense, attack, and damage.
And a Knight of the same level will lose to him; let's look at the characteristics:
The Knight has Tactics + Attack, and even if he takes Warfare, the Barbarian has an advantage: Warfare + Hand-to-Hand Combat, meaning that at level 2, he can already upgrade these two skills to level 2 or take Archery or Magic Resistance!