I am using it now, and it is fun so far. Don't know if I can finish the whole campaign with this mod on.

Will you consider release a version without increasing the enemy's health mate?

It's not an emergency, but I do believe it's these:
https://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=2670200255
https://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=2436464848
https://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=2433010130
I didn't do any thorough testing, but when these three were enabled, enemies were noticeably not seriously difficult. Most visible with the werebulls who would move at their vanilla SS4 speed.

what mods does it conflict with? I'll try and make a patch if you want

Returning to this so long later, I must say this is really, really fucking fun. Super fun. It's a shame it conflicts with enemy fix mods, but that's a very small price to pay for what this offers: Serious Sam 4 for super players. Glad it still works.

kamikazes run at tfe speeds

Daayuuuum, this is way harder now... but I like it! I just think that the Harpies and Kamikazes are a biiiit too fast now, but that's just my opinion.

Completed it. Reptiloids were probably the toughest.

I can't play without it now

I'll give it a go. Finished serious and punishing movesets are always nice

Yeah I did that part legit and without chainsaw launcher
You have to headshot the reptiloids fast and switch between killing zealots which now take two shots and brains
There is a decent amount of health in that arena so you can tank some homing projectiles but you have to play very well in that arena
I also killed the big worms with the shotgun to save ammo at the end maybe that will help you
Keep at it and you will beat it and become a better player :)

"The campaign was beaten 100% on serious without gadgets or upgrades to test balance"
I don't know man, is that true? First playthrough of Serious Sam 4 at the first patch that came out was without any gadgets, and without quicksaving. The furthest I got was the quarry battle, and that's when I had to break my rule; I had to use gadgets to win that fight. I'm all for a mod that adds challenge, but this sounds a little unreal.

good mod, makes enemies threatening and more fun. the enemies feel like the ones in the first encounter

You can make a mod where the enemies will only have new complicated attacks?
sorry about yandex translate

I like challenges