Well to be fair, no other girl group can compete with Twice. They're the new Girls' Generation in terms of popularity. Korea loves them and their fanbase is really big, just look at their album sales. They're huge by girl group standards. Actually, scratch that. They're huge by anyone's standards considering they are selling more albums than all the boy groups not named EXO and BTS as well
The only girl group that could potentially challenge them in the future is I.O.I, but we all know what's going to happen with them.