Every battle ended in tragedy.
There wasn't such a thing as a fight where nobody got hurt. It didn't matter who was good or who was evil, in the end, everyone would end up mourning someone they lost.
In this battle, that tragedy was even more prevalent.
There were indeed only 250 fighters on the Gehenna Tribe's side, and they were definitely weak by the standard of someone like Damien.
As he and his peers dealt with unreasonably powerful people and unreasonably talented geniuses on a daily basis, the average person would always appear weak to them.
However, the Gehenna Tribe wasn't necessarily weak.
Their methods may have had many weaknesses, but they survived in the cruel jungle for many generations for a reason.
Damien himself said it at an earlier time. The heights they'd reached with their backwards techniques were genuinely impressive.