Watcher has been terribly unappreciated on this board for the most part. Unless Thanos has a groundbreaking strategy, the Watcher can easily destroy him if threatened. Otherwise, it will just be a staring contest.
In terms of power, I would put the watchers pretty high up there, probably slightly above Odin and the Skyfathers..Maybe even much greater..
AAron the rouge watcher... for example... has fought Molecule Man, arguebly one of the most powerful guys in the MU..and defeated him rather easily.
Another Watcher that comes to mind is Utau..the one who resides on Earth 616's moon. He just stood there unaffected when Thanos was wielding the Infinity gauntlet and battling the other cosmic abstracts/beings. (That could have been because Thanos choose not to harm him though..)
Who knows how powerful they are..but I do believe they possess more than enough power to best Thanos in a one on one confrontation...
__________________ If knowledge is power..how come we have so many idiots in charge?!!
The only time I've seen a Watcher fight physically was in a What if comic (What if the Avengers battled Galactus), but this was the older version look of Watcher that looked like a WWF wrestler with a toga than a Gandhi. The newest version of Watcher would look awkward if he fought, but who knows? He could possibly do a Yoda for all we know.
Yes, they stand there and basically catalog, but they won't take a beating if it's meant for them. They're don't like getting involved, but they're also not stupid.
Uatu and the Watchers are a godlike race, their powers are probably equal or on the scale of those of the Celestials.I see a Watcher in troubles only during Abraxas saga when he take half of the medallion of the Watcher, that was in a suspended animation or coma like condition cause the medallion is some way connected to their lives.
Watchers are more or less as powerful as celestials, but they submitted all of their free will to the celestials so that they would not have to make any moral decisions and could not be blamed for any more tragedies (as they once interfered in the affairs of a lesser race, which resulted in the race destroying itself i a nuclear war).