That last GM kill done by Danan was brutal. Literally smashing it several times. No explosion to put the pilot out of their misery. Just the sheer painful G forces from that Zaku II smashing the GM with its fist and heat hawk.
Before Brown Southern Cross Corps showed up, the Federation Forces were able to push back against the Zeon forces with the GMs thanks to the combat data from the RX-78-2 Gundam.