If you have a weak omnimon, give him up. The most important thing is that their stats are high, so if the blackwargrowlmon is weak, don't get him. Also, omnimon is a mega and blackwargrowlmon is only an ultimate. If you train blackwargrowlmon to be level 63, have dark EXP of 25,000 or higher, and an attack of 360+, then you can dna digivolve it with diaboromon into a ChaosGallantmon.