This addon changes bane of arthropods to inflict a small poisonous splash every time you hit a mob with weapons enchanted with it.
This poison effect is different though, as it is the unused minecraft:fatal_poison effect that is stronger, and works on more mob types. Additionally, it can actually kill mobs as supposed to leaving them at ½ a heart.

Technical Details:
The radius of the splash is 2 blocks at base, each level increases it by 0.2
Every 2 levels, the strength of the poison is enhanced. By default, it's amplifier is 0, lvl 3-4 raises it to 1 and lvl 5 is amp 2
The duration of the poison is a fixed 3 seconds
The poison splash cannot harm the user, but it might be able to harm allies and pets!