Ultimate Waybig as shown in the Final Battle Part 1 and 2. Ther were some leaked pictures and so we know and also by some reliable resources.Little is known about him but we know some things which this blog is about.
Ultimate Waybig has 2 devil like horns protruding from the sides of his head.He has changed colours also,the basic colour change being blue and less red and white.His arms are white instead of red.He has a boots like pattern on his feet.
Little is known about his abilities too but what we know is all here:
His speed has increased and he is more powerful and durable.Lasers also dont effect him that much.He can fly now as you can see in this photo.Rumours are there that his size has also increased but i think that's nonsense because Matt Wayne said that they didn't want an any bigger Waybig.
Also he is the one who is seen fighting with Diagon in the last. And by that picture we can clearly see more of Diagon's full body. He does not just has an octupus like body but that's just his head. I hope you found it useful.
(As more information will come we will edit it.)