How much power does an air rifle need to kill animals up to the size of rabbits ?

Im looking into buying an air rifle and was wondering how much power I will need in both ft/lbs of energy and what that equates to in fps. I am on a budget so the cheaper the better! I live in England so am limited to 12ft/lbs of energy but would like advice on what to buy !

What is a VPN?

VPN is (Virtual Private Network) were first used by companies to enable their employees to securely access internal systems such as email remotely (e.g. from home or while on business trips). Today they are increasingly being used for personal use by individuals to protect their privacy while online in public places (e.g. when using the wi-fi connection in a cafe) or in a country where the internet is censored / blocked (e.g. China, Saudi Arabia…).