Optimal Aim mod
This mod helps you position your crosshair on other players for pvp purposes to help utilize your full 3 block reach by rendering a small, highly configurable cube on the best place to aim.
I made this mod because I see many new players aiming their crosshair at the other player's legs, losing a good 0.1-0.2 blocks of reach, when the closest point of the hitbox is usually the head.
Also if you set the max distance to '3', the cube will only render when you're able to attack the entity, useful for learning spacing and getting an idea for your own reach!

(More previews can be found here, at modrinth and check out Tektonikal's mods!)
Dependencies
This mod requires Fabric api, and Cloth config + Mod menu for configuration.
Is this a cheat?
No, this mod simply gives a visual aid that is limited to a maximum distance of 12 blocks away and only renders if you have a direct line of sight to the entity, this is not a form of ESP.