There is an amazing, family friendly, web comic by Scott Lincoln called Ralf the Destroyer. Ralf is sent in a massive planet busting spaceship to destroy the Earth, but he has doubts about the task he’s been assigned. He decides to take a quick look at earth first. As the story develops there are a number of other characters introduced including Lexi a 7 year old girl who explains that a friend would not destroy her planet. There are adventures with ‘men in black’ and an assassin who is trying to destroy Ralf.
At the moment ralfthedestroyer.com the original online home of the comic is not working (from inspecting the page it seems to have been broken with puppet). However it can still be found here at WebToons, where it can be read from the first episode through to episode 171.
The story is also published as a number of books that can be found on Amazon