It might take a while due to the sheer size and mobility of the Transformers + playing the ranged game, but I simply don't see team Thanos losing.
He is several orders of magnitude above a guy who can one shot kill a giant space whale that is larger and around as durable as almost any Transformer.
Iron Man had a flaming chunk of moon dumped on his head at speed that was nearly the size of a football field and was still capable of fighting. Can you see Bumblebee survive that? Honest question. I may have missed something. I only watched the first 3 films