MIGHTY THOR (1989) #461

The Dark Valkyrie has convinced Thor that he has always been Odins pawn, but no more; In Asgard, Sif senses that something is amiss, and seeks out Beta Ray Bill; They both use the Norn Stones and locate Thor, but he is no longer himself; He mercilessly beats on Bill until he is defeated, and Sif escapes; Thor declares that from now on, the only will he will follow, is his own.