Daryl wrote:RFC in the Starfire series used scorched Earth tactics to wipe out the arachnids (The Shiva Option). Ender destroyed worlds in Ender's Game.
Dr Who destroyed the Daelect world, and may or may not have destroyed Galifrey (depending on timelines).
While the Lensman series has been mentioned world destruction was a common ploy.
I admit to stumbling upon Ender's Game by accident. It is only found in the Young Adult/Teenage section in most libraries. I ran into a friend of mine who had her young son and daughter there to listen to a live reading. Her young daughter had Ender's Game in her hand after checking it out. She recommended it to me after having read it a few times herself. (Her mother was like "You're going to check that out... again?") I forgot there was planet killing in it -- be it somewhat downplayed as I now remember it.
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We should also note the Probe in
Star Trek: The Voyage Home.
The crew had to go back in time to retrieve a pair of Humpback whales to answer the call of the Probe in whale song. It was an impressive scene.It was to be five miles long and a mile and a half wide. ILM (Industrial Light & Magic) did a wonderful job on it. Pure unadulterated raw power. Each of the countless times I've seen that episode, I consider the long voyage of it. It was never depicted as traveling at any warp like speeds. It gave the impression that it took a direct line of travel to the Sol system -- completely oblivious to infringing upon any other species' territorial "waters," and gave the impression that any enemies encountered on its way didn't really matter.
ILM really did a bang up job on it. The Probe deployed what appeared to be a small moon when it activated. And the matter-of-fact consequences to befall Earth, had a whale not answered, would have been total destruction -- just by what was happening on the planet by incidental circumstance.
That episode stoked my imagination in more ways than one.
http://memory-alpha.wikia.com/wiki/Whale_Probe