Advice on how to reject a guy for the first time?

So after doing some online dating, I ended up talking to two different guys. Both of them are great. I recently went on a fate with each of them and now I find myself with a problem. I had a very clear connection with one, but the other one...there just wasn’t anything there for me. I don’t know if he feels the same way or not, but I just don’t feel like I could accept a second date. He’s a really sweet guy, and I did enjoy our date, but I just like the other one more. It just felt more natural with him. I’ve never had to turn a guy down before, and I really dont want to hurt his feelings. I’m so scared he’s going to get mad at me. Any advice on how to turn him down?