This one seems a bit hard for some, but it shouldn't be. Easiest way I found was run around without killing any enemies until you find one of the pods that spawns little spiders. Hopefully near the pods you should have a bunch of other enemies. Once you see at least 10 enemies go into AE form with and just attack () the hell outta the little buggers.
If you don't get it, it's pretty much impossible to not get it on the last level while fighting the Gorgon. When fighting, the Gorgon will spawn twenty or so mini-snakes. Just go into AE form and you shouldn't have the slightest problem getting a x10.