How we cite our quotes: All quotations are from Thor.
Quote #1
ODIN: Whosoever holds this hammer, if he be worthy, shall possess the power of Thor!
You always gotta read the fine print. Thor has some pretty massive power, but he need to earn it if he wants to use it.
Quote #2
THOR: As king of Asgard-
ODIN: But you're NOT KING! Not yet
A little smackdown from Dad here. Thor's been named heir and thinks that he's able to do as he likes: like marching on the frost giants and cracking some skulls. Odin, older, wiser and begs to differ.
It's also important that Loki's present for Thor's little temper tantrum. He says nothing. He just watches and listens. He's not nearly as powerful as Thor, but as we learn, he ends up holding a lot more power.
Quote #3
ODIN: The mighty hammer Mjolnir, forged in the heart of a dying star. Its power has no equal, as a weapon to destroy or as a tool to build. It is a fit companion for a king.
There's no question that Mjolnir has power, and Thor being Thor, is the guy who gets to use it. But Odin points out something really important here: the power of the hammer isn't automatically good or evil. Thor's choice of how he uses it that determines whether he deserves that power or not.