Thanos Feared an Attack From Odin and He Might Have Been Planning One. However, it's possible that Odin kept his kids in the dark because he was preparing to take on Thanos all along.
Odin, then, was a big opponent even for Thanos, so attacking Asgard would have been a huge risk and the Mad Titan could have been defeated, and he knew there would be other ways to get the Space Stone without risking his bigger plan.
With Odin still ruling Asgard, Thanos would have easily been stopped had he made a play for the Infinity Gauntlet. Odin himself had once sought the Infinity Gauntlet, and would therefore be attuned to any other individuals attempting to follow in his footsteps.
Thanos did truly fear Odin, it wasn't just the bifrost it was Odin's death. That's always been my head cannon. He waited for Odin to stop protecting the nine realms before trying to assemble all the stones at once. Ego had recently died too, so there was one less powerful being that might stop him.
We SOLVED Why Thanos Waited So Long to Pursue The INFINITY STONES | Marvel Theory
Was Odin aware of Thanos?
Thanos (Josh Brolin) then arrived during the end of his twilight days and annihilated half the universe, but the Allfather never manifested any evident sign that he knew about the forthcoming calamity. Some events could justify the king's silence, but they're not quite convincing.
I believe he was waiting for Odin (one of the most powerful beings in the universe) to die. In the comics Odin beat (or at least held his own against) Thanos and I believe that the reason that Thanos is only coming now could have something to do with Odin's death.
While Thanos is an Eternal and has the standard powers of super-strength, agility, regeneration, immortality, and more, Adam Warlock takes the upper hand. He can be killed, but he resurrects to be stronger every time.
If he was relatively calm Odin would probably engage the Hulk physically to underline the difference in power between them. Odin would crush hulk! Odin is the most powerful being in the nine realms outside of cosmic entities.
During the three years, Odin became weary of Kratos' presence in Midgard, fearing that the Ghost of Sparta could challenge his control over the nine realms or ruin his plans.
A significant part of Thor's trauma stems from his failure to kill Thanos in Avengers: Infinity War, leading to the Mad Titan's devastating Snap. Thor had Thanos comfortably beaten, yet did not strike a blow at his head, instead curiously deciding to sink Stormbreaker into the great Titan's chest.
Odin revealed that he wanted to gain a permanent peace between Asgard and Jotunheim by having Loki rule the world of the Frost Giants. Loki was disgusted by his own parentage and claimed that Odin could have never loved him the same way he loved Thor and would have never given him the throne.
In "Avengers: Infinity War," Loki fears Thanos due to their past encounters and the threat Thanos poses to him and those he cares about, particularly his brother Thor. Loki's previous experiences with Thanos likely left him aware of Thanos's power and ruthlessness, contributing to his fear of the Titan.
Because Thor spent too much time gloating that he was about to kill Thanos, rather than actually doing it, giving Thanos enough time to snap his fingers and get the hell out to heal himself.
Now Odin did tell Thor he was stronger then him (Odin) which some interpret as Odin meaning Thor is stronger than Odin cause Thor now has his fathers power plus his own. But we have to remember two things. Odin himself said Mjølnir only channeled Thor's power, Thor just needed to learn to use it naturally.
Odin stands a good chance at defeating a moderately-fed Galactus. Odin has been stated to be equal to a moderately-fed Galactus. Though Galan did withstand a powerful headbutt from Odin. The Devourer had just consumed one planet before that.
So while Zeus' best feat is defeating a mountain-sized monster, Odin's best feat is defeating a monster as big as nine worlds. Odin outclasses Zeus in intelligence, versatility, strength, and weapons. Zeus simply can't compete. The winner is Odin, All-Father of the Æsir.
But the one being Thanos hates more than anyone is the Merc With A Mouth himself, Deadpool – a rivalry that MCU fans are likely going to miss. While many fans may not expect this rivalry, Thanos and Deadpool have been at odds for quite some time.
Against Dormammu, Thanos without the Infinity Stones is already dead; it's only a matter of time. But Thanos with the stones? It all depends on where the battle is fought. In the Dark Dimension, Dormammu can win nearly any fight.
Thanos and Hulk have clashed several times in Marvel lore, with Thanos even admitting he was scared to face the Hulk before acquiring the Infinity Stones. While Thanos is usually the victor, it's generally down to him using superior tactics and technology, rather than simply possessing greater physical strength.
Loki cast a spell on Odin, and left him on Earth. But this is not the reason he died. Odin made it clear that it was his time. In the MCU this is the start of Ragnarok.
It turns out Loki had a real chance to survive Thanos, and it's possible that he did. Though Classic Loki made it past the Mad Titan, it's less likely that Hiddleston's Loki did. In the Loki premiere, the God of Mischief sees images of his entire timeline at the TVA, and the film ends shortly after Thanos kills him.
So far, that was the only film in the trilogy where Loki didn't "die." His final, final death came at the hands of Thanos in Avengers: Infinity War. Loki's parting words to Thor were, "the sun will shine upon us again." And it has, but in separate universes!
