Board Thread:Questions and Answers/@comment-32348174-20180608224219/@comment-13682699-20180804143229

The fallen humans were hinted at possessing the ability when you speak with Toriel after loading. Before that, then Asgore himself may have held the power but never realized it since he never died before then. The most likely candidate after both Asgore and the fallen humans but before Flowey is Undyne, but her situation would be the same as Asgore's.