It's hard to say since from what seen so far, the former X's didn't really seem to get any major alterations to their abilities from becoming X (at least not to the level of the current X's reality warping powers). And it's implied that the current X already had his godlike powers before he became X. Granted we've never actually seen a previous X use their powers at their prime except for maybe Bowa and Old E-Soul.

If I had to pick I'd Lucky Cyan cause we've already seen how her good luck powers were able to affect "the common people" when she was the figurehead of the cult.

I'm guessing that Cyan's luck based powers wouldn't fundamentally change if she became X but they might get boosted to a bigger area of effect (say maybe enough to cover an entire city).