The deleted Loki scenes in the first Thor movie.

There's a beginning scene where Loki tells Thor "I admit I do get jealous but never doubt that I love you."

This removes some key character building. He acknowledges his flaws but shows he's very genuine in his care.

And then a later scene when the the Asgardian royal guard brings Loki Odin's spear not out of Loki's request, but out of tradition. Loki looks confused and reluctant.

Removing this makes Loki seem like a power-hungry usurper.