I'm thinking of using a stun gun on my toddler who won't calm down.
Are you serious? Why would you use a stun gun on a child?
I'm not saying it's right, but I'm asking myself if it's worse to zap him or leave him be.
You should leave him be. Toddlers can get seriously hurt by tasers.
What should I do?
You should never use a stun gun on a toddler of course! You could injure or kill the child. Just let him calm down naturally.