Lapistia

I thought positive and negative reputation would cancel each other out and result in zero...

Negative reputation negates positive reputation.

But seriously, why x80?

Because when calculating, I forgot that the formula refers to the energy spent, not the total energy value...
Then it turned out to be (1500/15)*5*11+50% = 8250 damage for 100 energy (health), i.e., 1 unit of health was equal to 82 units of damage, while with the spear, it was 1 to 1.

I got confused in my own notes. But even so, the difference is still too large, despite the other features of the spear.