@SilverGalford: It was confirmed in the databook that the Tengen Toppa Gurren Lagann is 10 million light years tall (100 times the size of the milky way).
Hell it's even stated on the wiki present on this very site. At least do a search for these things before you post about how "100% Sure" you are that everyone else is wrong and only you are correct.
The fact that the Anti Spiral lost to them was due to the fact that it could not evolve to a higher level of power as the Anti Spirals had purged their spiral power in order to circumvent the eventual spiral nemisis. Spiral power throught the series was shown to grow with the persons will to win. Hence why the Tengen Toppa Gurren Lagann is nothing more than the manifestation of pure spiral energy.
As for the mind raping, They escaped from an extradimensonal labyrinth that the Anti Spiral trapped their consiousness inside, which is an infinite series of alternate universes.
As for the unlimited power, its made a point in the series that the stronger the resolve of the chartacter the stronger his/her spiral power is and as a result, the stronger he/she is. This is also the reason the Anti Spirals purged their spiral energy, because they realised that if they continued to grow stronger they would bring about the Spiral Nemesis. Spiral Energy is only as strong as their resolve, and by the end their resolve was strong enough to break free from the sea of dispare which convereted used spiral energy into pressure, alter probability and create a galaxy sized mech from nothing. All in all a good days work, given that they are simply "humans".
As for that thread you posted, Galactus is stronger than TTGL in base so there is nothing stopping him from taking them out quickly before they can grow stronger.
I would say Thanos would likely put up a good fight but he cant compete with something of that size and power without a gem or the IG.
I understand where you are coming from but to say he wins with the utter ease you suggest he does is just wrong.