Its not one or the other, either positive or negative.
He was both, as are most people, its just to what degree of both was he that's the question. Was he more positive, or more negative, or was he equally both?
The answer to that is in the individuals like myself who grew up on his music and his words.
Some individuals really took to the "Thug Life" mantra and bravado and really tried to live and embody it. In regards to those individuals I can say Tupac, his music, and general influence would be negative.
Then there are other individuals, such as myself, who could listen to him or his music with the ability to enjoy but ultimately disregard all the negativity while simultaneously being able to take in the intelligence, knowledge, vision, etc. that he possessed and learn and become better from it.
The truth is Tupac's life and contradictions were a physical manifestation of our community, us as a people, and the good and bad of both.
So the part of Tupac that you gravitate towards and were influenced by is essentially a result of who you were/are.
If you were/are a thinker who seeks knowledge, had a desire to learn, cared and were concerned for your people/community that aspect of Tupac would attract you.
But if you were an individual who was drawn to the streets, bravado, violence, drugs, misogyny, etc, then that part of Tupac will be what you would gravitate to.