Distance from an object to a all raycast or all box collider

Hello,

In a top down twin stick shooter. I would like to do an auto aim for improve the game feeling with the stick.

So I drew visually thanks to a mesh renderer a line that is child of the player and indicates the forward direction (facing him).

Now, either using a raycast or a collider (browsing the whole line) I'd like to be able to say.
If the enemy is near the raycast or the collider then I hang the target on the enemy.

I tried with a magnitude but it takes the base of the line whatever happens. I'm giving you an example below.

Thank in advance.

Alexandre

 

This is unrelated to navigation, you're posting in the wrong subforum.
However, this link should answer your question.