At this point in the MCU, we don't really have any frame of reference for truly how powerful Thanos is. He hasn't been involved in any of the action, but we know he has been the master manipulator behind all of the happenings surrounding at least the Tesseract (from Captain America: The First Avenger and The Avengers), the Power Stone (from Guardians of the Galaxy) and the Mind Stone (the gem in the scepter that was granted to Loki by Thanos in The Avengers and had its true power unleashed in Age of Ultron).
As it stands, his stature is simply "implied badassedness" since both Loki and Ronan (the only two villains from the MCU to have direct contact with him) both appear to fear him.
That said, his machinations are thus far ultimately thwarted - he sacrificed the only Infinity Stone actually in his possession (the yellow Mind Stone, contained in the scepter) in a fruitless effort to procure another one (the Tesseract, which contains the blue Space Stone), then drafted Ronan to retrieve the Power Stone (purple, contained in the Orb), which also failed. This is why we see Thanos in one of the 'stinger' scenes at the end of Age of Ultron begrudgingly reach for a gold glove (the Gauntlet) and state "Fine. I'll do it myself."