Thanos vs 1 Celestial (my added comment)
A while before I joined this site, I saw a forum dedicated to discussing a battle between one Celestial and Thanos. The forum had the set rules of round one featuring no preparation and round two featuring preparation. I'd like to add my comment since the thread is closed.
I say that without preparation, the Celestial wins the battle. With preparation time allowed, Thanos wins the battle. Here is my reasoning for both.
A lot of people mention the Odin vs Thanos battle being a stomp in Odin's favor, which made me wonder if anyone had even read the comic it was featured in. Thanos was not fighting Odin to beat him, Thanos was fighting Odin because Odin would not listen to invaders bringing his defeated son to his doorstep. It was clear throughout the battle that Odin was trying to kill Thanos while the other isn't true. Thanos actually tanked several of Odin's blast before Odin summoned his spear. He also made Odin stumble around a lot during the beginning of the fight. So, some people saying that Thanos couldn't lay a scratch on Odin are lying. The fight was closer than many people on this bored make it seem. That being said, Odin would have won the battle, even if Thanos was serious about trying to beat him. It's be very close, but Odin Force is too much for Thanos to put down.