There are those that have seen the Thor movies and those that have seen The Eternals most likely and might think that Ikaris would surely give Thor a run if not obliterate him entirely. The thing is that in the comics, Ikaris stands no chance and he knows it. In The Eternals, there’s actually mention of Thor as one of them knew him when he was a boy and laments that the god of thunder doesn’t even call him anymore. Given that the Eternals stayed out of the fight with Thanos due to some hypocritical jargon laid down by Arishem, it’s likely that Thor might not have thought too highly of them for a little while. But considering (spoilers) what Ikaris did when trying to keep the Emergence from being stopped, it’s fair to say that he and Thor might not be on friendly terms any longer since Thor has come to value the people of Midgard over the course of the movies he’s been part of, and might have smacked Ikaris upside the head a few times to try and bring him out of his funk.
I can almost hear people talking now, perhaps saying something along the lines that Ikaris would throw Thor around like a rag doll and perhaps even see how sturdy Stormbreaker really is. Quite honestly, that would be kind of amusing since even with his powered down form Thor would likely have a better chance of knocking Ikaris around without too much trouble. The fact is that in his current form, meaning his out-of-shape form that the audiences were left with, Ikaris might be able to put up a good fight and keep his distance while taking Thor to his limit. But when the fight gets going and Thor really starts tapping into the power that’s at his disposal, Ikaris would find that the god of thunder is well out of his class, since like it or not Ikaris is who he is and that’s about as good as it gets.
Unlike the Deviants, he doesn’t evolve, since once he’s killed his consciousness is transferred to another body that the Celestials have ready to go. And while he does have a tremendous amount of cosmic energy at his beck and call, Ikaris is still outmatched since Thor might not be a better fighter than he is, but he’s definitely just as tough and far stronger. Plus, it’s already been seen that if Ikaris has his purpose stripped from him, or if he’s made to question his actions, then he becomes a wreck. It’s true that Thor’s not much better in this regard, but in his anger, Thor is a lot more dangerous than Ikaris since his power level will jump from the base level to an extreme that the Eternal won’t be able to contend with. What’s amusing about Ikaris is that for all his power, he’s not capable of unleashing it as Thor is unless he has a desired direction and directive to do so. Ikaris is more or less a servant in the MCU who is bound to follow orders, while Thor is a free-thinking individual that doesn’t bother with what others want unless his goals are aligned with theirs.
It would be easy to say that Ikaris is a little too arrogant in the MCU to really be that big of a threat to Thor, who was arrogant but calmed down quite a bit over the years as he learned the value of humility. Entering a fight at this time in the MCU it does feel as though the two combatants would be separated by a great deal of attitude since Thor would no doubt enter the fight with the thought of how to come at Ikaris while the Eternal might think that he could simply blitz the thunder god and call it a day. While it’s true that both men are great fighters, in the MCU it would appear that Ikaris has fought mostly Deviants that are seen to charge forward more often than actually come up with a battle plan. While Ikaris could keep his distance for a little while, Thor has the ability to fly as well and wouldn’t necessarily give the Eternal that much room to think, let alone make a solid battle plan.
At the end of the day, these two are close to being evenly matched in a few ways, but a lot of people feel that despite the fact that he’s definitely younger than the Eternal from a technical standpoint, Thor is definitely stronger and more capable of carrying the fight. There are bound to be plenty of arguments that would say otherwise, but in the opinion of many, the thunder god would be victorious at the end. In fact, the only real advantage that Ikaris has over Thor is that if he dies, he’ll come back in yet another body thanks to the Celestials.