Translation for a tattoo
Despite the cynic fever on tattooing Chinese characters on one's body, let me try to help:

幸运混蛋（Simplified Chinese）
幸運混蛋（Traditional Chinese）

They are correct translation for Lucky Bastard. But when someone reads it, it sounds a bit weird.
Maybe you could consider this term:

混世魔王

It means a demon/monster king who disturbs the world.