I can agree that the Valar choosing to completely destroy Numenor (given Tolkien’s assertion in the Letters that the power to do so came from Eru, but the Valar chose the method of wielding it) does seem like overkill, but I’ve generally just shrugged because Tolkien wanted his Atlantis. (I mean really the Numenorean fleet was not a substantial threat, just destroy the fleet and leave the island alone, that’ll probably take out the leaders anyway.) However, the Valar are as a rule not the type to take that sort of aggressive action. Even leaving aside that I firmly believe the Valar to be fair and just rulers, I just can’t think of any other time they take action that abruptly and dramatically. That leaves the question of why, exactly, the Valar chose to wipe out Numenor, and particularly in that specific and dramatic a fashion.