User blog comment:BarrelHornet3/Hidden Kill Count for Pawn Bestiary Knowledge/@comment-11766885-20130920165008/@comment-5166842-20131001145541

Not that I've seen. If the 3rd star is eluding you for a certain enemy just check its page. If the info isn't there, ask in the comments.

Assuming you play the game enough that kill count isn't a problem then it's a pretty short list of enemies you'll have trouble getting the 3rd star in.