If it has feelings, can feel pain or suffer then I think it's wrong to actively choose to kill it (I'd include insects). Obviously if it's done accidentally then I don't have a huge problem with that and the exception would be if you literally had to kill an animal to survive, then not only would I be fine with that but I'd probably do it myself.
As for whether it's okay to kill cruel meat eating animals, well as I tongue-in-cheek pointed out to MattP in this thread months ago, he along with plenty of other human meat eaters would be high up on the list.