rapture-in-red:

Character development

Loki really has the best character arc in the MCU.

• In Thor, we see years of seething envy, spill out, magnified by the revelation that he is both adopted and a Jötunn; all of his insecurities seemingly confirmed and justified.
• In Avengers, we see him at his rawest, and angriest after the events of Thor.
• In The Dark World, we start to see the cracks in the facade of cold villainy. The shock at Odin’s condemnation, his intense love for his mother and the grief at her death, and above all, his clear happiness and excitement to be adventuring with Thor again. I left the theatre with the feeling that his warm praise of Thor in Odin’s guise might actually have been sincere.
• In Thor Ragnarok, three things happen; Odin finally tells Loki he loves him. Thor and Loki become equals in a secret that Odin withheld from them both. Most importantly, Loki, who has felt like he was second best his entire life, finally realises that someone always loved him more than anyone else, and that it was Thor the whole time.

Which brings us back to Infinity War. At long last, Loki no longer feels aggrieved, and is comparatively content with his place in the universe. He dies defending the one thing left in the world that he loves.

That there is brilliant character writing and acting.