>>19639241People here are mentioning Aquarion and Demonbane both of which are worthy competitors, but I think that the Granzeboma (The Anti-Spiral Mech) that appeared in show itself, was in fact more powerful than the TTGL.
It not only showed combat capabilities that are on average surpassing the Gurren Lagann (both in the combined and the non-combined form), but it also seems to be much more durable.
Both in the series and in the movie, Simon had to go for a direct impact with the cockpit, because that was the only way he could truly destroy it.