Ok how can I tell a guy I just want to be friends without hurting him .make him hate me or be mean to me

How old are the two of you? Have you been dating?

No he is a friend and younger than me I a 14 and he 13

Why "just friends" now? What has changed?

Okay, well if he is just a friend, then what's the problem?

If he likes you, is going to hurt regardless, but leading him on will always hurt more. Tell him just like that, "I only like you as a friend".