"Your kind is considered a delicacy where I come from!" -> Standard one, to be used against anyone.
"When I saw you [insert plural species name] for the first time, you were nothing more than pitiable piles of flesh crawling around in caves and devouring the dirt from the floor!" -> Use against former pre-sentients for maximal effect.
"Yesterday I scrunched a bug with my foot. The spot on the floor had some stunning similarities to your face." -> Especially against insectoid species.
Aliens to Humans:
"Your body is as ineffective as... nope, there is nothing comparable to your body's ineffectiveness."
"Our first researchers believed that the apes where version 2.0 of humanity... that theory seems to be correct."
"There are two kinds of humans: The first kind will be dead in one month. The second kind will be dead in two months."
(After defeating them in a war) "Humans: They go into the desert, but die because of heat. They say that aliens are dumb, but they can't colonise anything that's not perfect for their bodies. They go to space and die there, because they don't know how to use airlocks properly. But sometimes they are quite effective: They concentrate their forces at places where our fleets would arrive months later, because they are engaged in taking their undefended homeworld."
"Humans are strange beings, you know. They call their homeworld 'Dirt'! And also, in their last economic crisis they told everyone they didn't have any food, but they had at least five pets in every single building!"
"Surviving one world war is okay, but surviving two of them in the same century...!?"
"Why didn't that Third World War you always talk about happen? Life would be so much easier on Earth without you humans infesting every corner of that otherwise beautiful planet!"
"Oh, did the humans once again have one of their 'good ideas', huh? Like last year, when you just blew up your own colony with a mining ship? That's not bad luck anymore: That's just stupidity!"
