Hes still weak willed and has changed his end goal 3-4 times. Ninjas percevere, and that ***** aint percevering with his goals.
But ya he didnt get manipulated as much as most say, BUT PERCEVERING AND STUFF
Changing your mind doesn't mean you're weak willed. Sasuke had good reasons to change his goals but he always follows them without remorse. He has showed conviction surpassing Naruto at times.