Collision OnTriggerEnter2D damages multiple times!

When the player swings the weapon and it hits a monster it damages it multiple times per one swing.
I’ve tried to add a bool to restrict it to one damage per collision, but that fails to work if there are multiple enemies within the swing as it only damages the first one hit.
My current code on my weapon object is something like

    private void OnTriggerEnter2D(Collider2D other)
    {
        if (other.gameObject.CompareTag("monster"))
        {
            other.GetComponent<Monster>().Damage(wdam);
        }
    }  

How would I make each monster hit take damage once per swing?

@DerpMooseFish I’m gonna assume that you only have 1 player the bool you have shouldn’t be in the weapon but in the damaged enemy “Damage” would have a bool. That’s a quick solution
if there’s multiple players though we’d need to discuss that further.