The Breach enchantment causes protection IV leather armor and protection IV netherite armor to protect nearly the same amount, so much so to the point that with Strength 2, a player wearing either leather or netherite armor will take 4 critical hits to be defeated.

This would not be the case if Breach negated armor less (ie: -5% per level rather than -15% per level), and the mace's base damage was higher instead (ie: 11 attack damage rather than 6 attack damage).

In the attached video, both skeletons, one wearing prot 4 leather and the other wearing prot 4 netherite, take 4 critical hits with a Breach IV mace and Strength II to defeat.

Steps to Reproduce:

1. Spawn two skeletons with no AI that can pick up loot

   /summon skeleton ~ ~ ~ {NoAI:1,CanPickUpLoot:1b}

2. Give the skeletons full prot 4 leather armor and full prot 4 netherite armor respectively
3. Give yourself Strength 2 and a Breach 4 mace
4. Observe that both entities take 4 critical hits to kill, even though one is wearing leather and the other is wearing netherite

Expected Result: The skeleton wearing prot 4 netherite takes more critical hits to kill than than the skeleton wearing prot 4 leather when the user has strength 2

Observed Result: Both skeletons take 4 critical hits to kill, due to the overtuned strength of the Breach enchantment combined with the undertuned base damage of the mace