so a while ago I transferred ho-oh to my black 2. I feel a little guilty so I want to know will
ho-oh come back?
No ho-oh will not comeback sense you get it just once in the game and its the games legenadry Pokemon and legendary Pokemon mostly are unique in each game they appear in although you would be able to get lugia in HG if it makes you feel less guilty. But no it will no appear again
No. Once transferred into a newer generation, there is no way to get a Pokemon again in the old generation; with Ho-Oh, you can't get it again unless you restart the game.