If you go to iCloud.com, you can delete any contacts that you don't want to save in the cloud anymore, but I caution about deleting all of them from iCloud, because then they are removed permanently. Its a little easier online, but you still have to do it one at a time. There are some apps from the app store that can help you delete them as a group or organize them better. Unfortunately, iPhone and iCloud don't let you delete multiple contacts, unless you erase the entire device.