Would Hindus consider certain animals such as crocodiles as "Evil"..since they greedily devour other animals?

No, because it is their nature to eat animals, they cannot eat plants, that is bad for them. It is the cows nature to eat plants it can't eat animals, because that is bad for their health, and they can't physically eat them either because they are not built that way. We think cows are sacred because we think of it as mothers (gomatha: go=? matha=Mother) because it gives us milk, and is patient like a mother. "do they ever go back to being animals?" (I didn't understand the question before this) Yes humans can become animals (in their next life) if they have accumulated bad karma, by doing things an animal would do...