This is significantly better than Vicious Conquistador which is an uncommon. This should be toned down and put up in rarity, but seeing as that would unsymmetricalize your cycle maybe reinvent this?

Considering the name, maybe something about disabling blocking?

Maybe target creature with cmc or power 3 or less cant block

maybe up to two target creatures eith cmc or power 2 or less cant block?

lots to do here. Losing life might not be best placed here :D

this isn't really better than Vicious Conquistador but i can tone it down. These all have to be commmon, so I can't change that.

I still stand by repeatable life loss being too good at common. See my comment on Nyxfallen Skink

yes, but this card is basically crap, and most people wouldn't play it. Since it is 1 life for 3 mana, and i cant up rarity. I think it is just gonna stay how it is - weak.

strength isnt really what decided rarity. Commons are allowed to be good, and should be. It's just the subject matter that might not want to be at this rarity.

You can keep it like this if you like, but it might be sub-optimal design flavor wise. I suppose mechanically it's actually okay, just not very interesting. This also hits you and feels weird to pay for.

Might actually be cooler as a triggered ability, but that would break your cycle. Would be cooler to see something else other than lifeloss and burn on the black and red card in the cycle. Uninspired, but acceptable.

the idea is that it scares people. So life loss = Fear (jumpscare heart attack whatever)

Life loss isn't fear, life loss is more like being hurt, well that's what life loss IS. Fear would actually be much better represented by preventing blocking. If this ere Nyxfallen Lacerator or Nyxfallen Slicer than it would be appropriate.