The ten years of the Marvel Cinematic Universe have presented some compelling characters and relationships. However, perhaps no relationship in the MCU is as compelling as that of Thor and Loki. The struggle between these two brothers drives much of the MCU’s conflict — it’s even the catalyst for bringing together the Avengers.

Now that INFINITY WAR has — potentially — ended this dynamic for good, we want to take the chance to look back on Thor and Loki in the MCU.

THOR Introduces The Brothers

We first meet Thor and Loki in THOR. At this point, they are young and still figuring out who they are — Thor is a little brash, and Loki is a lot insecure. Thor is set to be crowned the new king of Asgard, and Loki is jealous. He doesn’t understand why Odin favors his brother — but will soon find out.

When Loki’s tricks send Thor and his friends to Jotunheim, Loki learns a terrible truth: he is not actually Asgardian, but Jotun. He confronts Odin, who reveals that Loki is not his son, but his enemy’s — Laufey. Now, Loki understands why Thor is favored: he is Odin’s real child, while Loki is a hidden monster.

That conflict drives the dynamic between Thor and Loki in this movie. At first, the dynamic is mostly one of sibling rivalry and jealousy. Thor is the golden child, and Loki craves Odin’s approval. When Odin reveals the truth, however, Loki’s internal conflict sours his relationship with Thor. He still loves his brother, but his self-hatred causes him to lash out.

The big showdown between Thor and Loki isn’t even really the main conflict in THOR. The real issue is Thor maturing and learning how to be a wiser king. But THOR plants the seeds for this brotherly relationship to crash and burn spectacularly in the next movie, AVENGERS.

AVENGERS Brings the Hate

Tom Hiddleston has said in an interview about Loki’s motivations that the opposite of love isn’t hate, it’s indifference. According to Hiddleston, that explains Loki’s actions in AVENGERS. Loki cannot be indifferent to Thor because he still loves his brother. But his jealousy soured after THOR and turned into hatred. He wants to make Thor suffer like he suffered.

For his part, Thor is maturing. He knows that Loki’s actions on Earth are a backlash to their childhood. Therefore, he feels it is his responsibility to stop Loki. At the same time, he cannot hate his brother. He defends Loki from the other Avengers — there’s no indifference here, either.

The big takeaway from AVENGERS is that the relationship between Thor and Loki is so messed up that it causes serious consequences. Their twisted love/hate dynamic forced Nick Fury to assemble the Avengers. So much of the MCU would not have happened had these two just gone to family counseling.

THE DARK WORLD Complicates Things

After his actions in AVENGERS, Loki must face justice. That justice is perhaps the cruelest thing he could face: indifference. He has now lost Thor’s love, but cannot even inspire hate. Instead, Thor ignores Loki when he is imprisoned and moves on with his life. Loki still loves Thor, in his own messed up way, so it hurts.

Things get worse when Loki loses the only family member who does still love him, Frigga. However, her death serves a greater purpose, and I don’t mean saving Jane Foster. When Frigga dies, Thor and Loki are brought together in mutual grief and a quest for revenge. They are not both Odin’s sons, but they are definitely both Frigga’s.

THE DARK WORLD also shows us a real dynamic between Thor and Loki. The scene where they are fleeing the palace, hunted by Asgardian guards, shows that they are actually brothers. The bickering is totally accurate to how siblings fight over the littlest things, but still, support each other in the end.

When Loki “dies” on Svartalfheim, it shows that Thor was never actually indifferent. Loki gives his life to save Thor and Jane, and Thor appreciates that. He swore that he would never trust Loki, but cannot stop loving his brother. Of course, he’s right not to trust as Loki is not actually dead and takes over Asgard when Thor leaves for Earth.

Old habits die hard.

RAGNAROK Gives us Peak Thor and Loki

Fans of the relationship between Thor and Loki finally get their payoff in RAGNAROK. The film fully captures the complicated relationship between them but never undermines the love they share. Finally, we see what can happen when Thor and Loki work together — they may not trust each other, but they love each other, and that’s enough.

We finally see what Thor and Loki are like when they are not actively fighting each other. They snark back and forth like real siblings. They work together, whether to stop Hela or to escape Sakaar, with the fluidity of years of experience.

The elevator scene was a gift from Heaven. They actually talk about their feelings — shocking, to say the least. Thor admits how much he loves Loki; it wasn’t one-sided affection. When Loki betrays Thor, he takes it in stride because it’s what he expects. However, he also never doubted Loki’s loyalty. When Loki shows up to save the Asgardians, Thor shows no surprise, but only remarks that Loki is late. He always knew Loki would come through.

RAGNAROK also gives us a satisfying conclusion to their arc. In THOR, they start off as brothers, but there is unspoken tension. Loki is jealous, Thor is oblivious. AVENGERS shows how dark their relationship could be if they give in to hate; THE DARK WORLD shows the futility of indifference. But RAGNAROK shows what could be if they allow themselves to be brothers. They can save the world if they work together.

And they can be happy.

INFINITY WAR Kills Everything

Of course, they’re not happy for long. After finally settling into who they are supposed to be, working together, and saving their world, things cannot end well. Thanos comes along to destroy us, emotionally. But INFINITY WAR underscores how important this relationship finally came to be to both Thor and Loki.

Loki gives up an Infinity Stone to save Thor’s life. He tries to act indifferent, but Thor is too important to him. Thanos knows Loki’s weak spot — his brother. The opening on INFINITY WAR also shows that we were so close to seeing a healthy dynamic. Loki identifies himself as an Odinson, finally accepting that his birth means less than his upbringing, and how important his family came to be.

When Thanos kills Loki, we see that he was not the only one to treasure the family dynamic. Thor spends the rest of INFINITY WAR trying to avenge his people — but specifically Loki. He wants to make Thanos pay for killing his brother right when they had finally figured things out. It doesn’t quite work out, but it’s a compelling motivation as Thor tries to avenge the person who means the most to him.

Thor and Loki Will Break Your Heart — In The Best Way

Of course, after INFINITY WAR there are numerous theories stating that Loki is not actually dead. The film gives mixed signals. Loki tells Thor the sun will shine on them again. Thanos explicitly states that Loki is not coming back this time. Thor seems unsure, hoping that Loki will return but unwilling to trust again.

Regardless of whether or not Loki is alive, though, it’s undeniable that Thor and Loki are some of the most compelling characters in the MCU. Their struggle to accept who they are drives so much of the story, but it also pulls at your heartstrings. Odin’s sons, and their meandering path to peace and love give so much depth to the MCU.