It's very possible he'll be attacked because he's vulnerable and the new guy, so he hasn't established his rank in the tank's heirarchy yet. What size tank do you have?
I don't want to be the mean one here, but those are a lot of fish for one tank. You'd need several hundred gallons to make that work. I'm also worried about the fact that you added that fish with zero quarantine, putting all your other fish at risk for disease. Believe me, skipping quarantine doesn't seem like a problem until you have an outbreak of ich or other parasites, then it's an absolute nightmare because you can lose all of your fish quickly. Please think about investing in a quarantine tank in the future.