Most Helpful Guy
Most Helpful Girl
You aren't going to not hurt his feelings. You can however make it so he understands that it isn't just him being "not the socks you want."
Just tell him that you don't feel you guys are connecting. Tell him you like him but just don't see you two going anywhere together and assure him that it isn't necessarily his fault and he isn't a bad guy. If he tries to negotiate (most people will) stand your ground and tell him you really thought about this and made up your mind and want to move on and that you're being upfront with him to save him any games.