>>7431502He did, that's why the Valar decide to intervene and start the War of Wrath, remember?
In all seriousness the Silmarillion was written from collections of his notes that were probably never intended to all work together, so maybe Tolkien planned on retconning his power level or weakining him post exile.
I also think it's less to do with him being scared, and more to do with him fearing for his own armies, in the first battle, ALL of the orcs are killed, and being the mightiest of the Vala wont help you much if it's just you vs a continent of angry elves, and you are bound to your physical form.
But I think it is also canon that he was a massive coward, so there's that.
