Another toddler keeps hitting my child at a public activity — how should I handle it?

Explain to your child out loud when it happens “that was unacceptable he should not hit you like that you did so well not hitting back if he can’t play nicely you tell him to go away ok”
Say this loud enough for the mother to hear and say directly to the parent I understand accidents happen but this type of play is unacceptable please don’t let it happen again, thank you

This is the only thing I find that works at any activity when a child isn’t being very nice either hitting or name calling or anything

I always correct the child directly with a firm ‘no thank you, we use our gentle hands while we’re playing’. And try to catch the eye of the parent with them so they see and hear me. Also taught my daughter to say no thank you, I don’t want to play like that and to move away if others are hitting.
I understand it’s developmental and a lot of children go through it but if it’s happening every time I would perhaps quietly ask her to please redirect her child to a different area or toy if they cannot play without hitting.

You can't control how others parent, all you can do is teach your child and guide them in the way you see fit. All the behaviour this child is exhibiting is developmentally normal, and if she wants to be gentle about it that's her choice. Honestly I don't think talking to her would make a blind bit of difference to how she handles it so I'd focus on your interaction with the child. You don't need to tell them off but you can stand up for your child without putting the other child down. "That wasn't very gentle, we're going to move away and play somewhere else if you can't play nicely". She'll soon appear if she doesn't like the way you're speaking and you can calmly say "it's none of my business how you parent but it is my business to look after my child so I'm not going to just sit here while this happens, I'm going to intervene". I'll also say, it's 2 year olds interacting with 2 year olds. If you're going to try to relax you have high hopes!! If not this one it will be another...

Try to place yourself far from them.

If he wants to hit him, with his mum around or not, stop his hands and protect your child, tell him "that is not OK". Say out loud "gentle hands, gentle hands, we don't hit". That should make the mother react.

If the boy keeps hitting, talk to the organizer. No matter the age, mothers should be able to keep their children under control.

We love going to indoor playground and had kids hit and push my girl. This might sound mean,but i don't look for the parent of the child I go to the child and use a firm tone and tell them do not hit or push. A lot of times the kid is surprised by my firm tone. And afther that I noticed the kids would avoid my daughter because they know I will be firm to them. I use to do the tell the kids nicely to not hit,but that would not work and we would walk away,but that would also not work.

I'd tell the kid to stop directly if the parent is not acting enough.
Our little children can't express and protect themselves very well yet, we're there to protect them. Just like if someone try to hit you, you'd ask that person to stop directly.
My job is to protect my child, not to care about another child's feeling in the expense of my child getting hurt. And I don't mind the social awkwardness.

And I wouldn't take my child away either, unless she wants to. She has the right to play there without being hit.