Though there is no first, second, or third-hand knowledge of his having done so, his imprisonment here surely offered him enough time to ponder his wrongs. But there is no evidence of his having suffered regret in his actions--- even of today.
But if at all, there is--in the Entirety of All That Is--one thing he wanted most to possess [enough to proffer a Bargain with Antagonist No. 1], and he may well regret sending her through the Window of Light, and into a displaced fragment of Time. Especially by the Third Displacement. But then he is the originator of what this world knows as the If-I-Can't-Have-Her-Then-No-One-Will Syndrome.