>>5959021Primus and Unicron, obviously - then Galaxy Force Starscream, Energon Galvatron and Omega Prime since they swole to planetary size;
Canonically, Metroplex and the other Titans are the largest Transformers in fiction after planetformers, at about two miles tall, and Trypticon is about the same size.
Metroplex was described as 800 metres tall in some ancient Japanese magazine.
Fortress/Brave Maximus from 'Car Robots' is about 500 metres tall.
Tidal Wave from Armada should be about 600 metres tall, given that his arms alone combine into an aircraft carrier comparable to Broadside and of a type which, in real life, is over 300 metres long.
In the G1 cartoon, Metroplex, Trypticon, Fortress Maximus and Scorponok were a good deal smaller, at maybe 100-150 metres each.
But then Unicron and Cybertron were also wayyyy too small, so...
