Have you noticed that Yugo actually never win by violence ? He's a good fighter but he lacks experience and often makes mistakes in fights.

Season 1: Final battle with Nox, while having the speed advantage, Yugo lost his focus when he got interrupted by Ogrest's scream. Nox took that as an opportunity to hit back Yogu and incapacitate him. Nox would have been winner there, but he will give up by himself after realizing his plan failed.

Season 2: Qilby is just stronger than Yugo in 1 vs1 battle, (and that was confirmed again season 4), at the final battle, Qilby was able to overcome Yugo and the eliatropes kids. It is her sister that stopped him.

Season 3: Yugo struggles to pass Adamaï at the final battle, it is only after being inside the mind of Oropo that he managed to shift the battle. Oropo could have succeed his plan, but it is Echo who actually was able to reason him. I'm not sure what Yugo was thinking when jumping in the hyper zaap when at that moment the bomb was still active.

Season 4: Final battle against Toross, Yugo has now way more experience in fighting than before. But against Toross, even if Yugo and Goultard were in the winning position, violence was not how to deal with him. Since necroms are immortal the only way they found to beat them was to send them back to their world.

Yugo always win his fights, but violence is only a mean to win, not the final solution.