He could just say something like, "I just have to do one little thing to make sure that you won't interfere with my plans", and cue the attempted Glaciate.
As far as the scene goes, it's a mere few seconds. Nothing for anyone to worry about in terms of censorship. As far as dialogue goes, I'd rather he not say "destroy", it just sounds lame. If they have to avoid the word "die", "kill", or "murder", then something like what I wrote above could work.
Besides, in a cartoon like Adventure Time, those words are said all the time. The main character is a hero who slays monsters and baddies, and there's even an episode or two involving murder mysteries (granted, both cases were just the hero's best friend playing tricks on him, but the word murder has been used on that show a bit). I don't think anyone's had a problem with that, so they shouldn't have a problem with the mere mentioning of death in these games. The scene is extremely brief, anyway.
Oh, youth... guided by the servant of the goddess... Unite earth and sky, and bring light to the land.