Actually it has been speculated for some time that the orb that thanos was in perssion of somehow amped his abilities.
To the former picture, Galactus was as stated earlier, back a second later I quote Thanos "I would be a fool to think that my Attack did ANYTHING but to enrage Galactus" And in the next scan Galactus was back in force and with one blast pierced all the shields Thanos had activated and Galactus himself stated that a second blast would kill Thanos. Also from what I know Galactus was believed to be feed but that statement comes from a conversation between Thanos and Galactus in the astral Plan where it is hard to gauge Galactus powerlevels (I think).
Anyway Tyrant for the win.