Buttercup is the tough and hardcore one of The Powerpuff Girls. She acts like the rackless one of the team. She has a deep tomboyish voice. Normally she's tough and mean but is a girly girl deep down inside. You can use the original Powerpuff Girls version voiced by Elizabeth Daily as a reference, you can reference The Powerpuff Girls Z English dubbed version of her if you would like, or can combine the two voice to make up your own version. Remember to stay true to the character.