I noticed that in the egg moves, that it could learn Mega Horn and to my surprise, also Drill Run. So I'm just curious, how can it learn them two moves by breeding, or should I move a Pokemon that is breedable to the Karablast, teach it Drill Run via a move Tutor, then switch it back to Pokemon and let it level up to learn Mega horn?
You could breed a Male Karrablast with Megahorn, to a Female Karrablast with Drill Run.
Alternatively you could also breed a Karrablast with both Drill Run and Megahorn already (get Megahorn through breeding and Drill Run through tutor) and breed it to a Ditto/any Pokemon in the Bug egg group.
Hope I helped!