Here's part of a letter that Tupac wrote to Madonna that was being auctioned, until Madonna sued the auction house and the consignor claiming it was her property. You won't get a better confirmation of authenticity than that!
Here's a close-in crop of the autographed area of your Tupac:
Tupac was left-handed, which is usually evident in genuine Tupac writing and signatures, and is evident in the Madonna letter.
Comparing them, what do you see?
Compare the angle of the writing to yours, since there's a lot of it.
Then compare how he signed "2Pac" to yours. Since that's only one example, the three paragraphs of handwriting are more reliable for authentication purposes.
Study autographs objectively, not biased towards them being genuine or not, and you will learn how to be your most reliable authenticator.
That doesn't mean don't show it to others, like members here, but you can make a quite reliable decision yourself over time as you learn.
Tupac's writing generally has a significant left slant. That's clearly evident in his letter to Madonna that I posted.
The inscription "Keep ya Head up" on your Tupac piece has a very noticeable right slant. The "Pac" of 2Pac also have a noticeable right slant.
Even before we get into the letter shapes and other characteristics, that makes me feel strongly that yours was not autographed by Tupac.
Sorry, I know that's not what you wanted to hear. Other members may have different opinions on your Tupac. We'll see.
Someone sent me a video showing Tupac signing with his right hand, and there are other examples. What's strange is that Tupac was widely reported to be left-handed, and his provably authentic writing almost always has a strong left slant like left-handers often have.
But while that question is up in the air, the angle of his provably genuine writing is not. It looks like a left-hander's writing. Really strange.
The COA is from Brian Slavin of Autograph Central. Here are some discussions about him:
That picture was taken September 4, 96 at the mtv awards. It’s not on a Polaroid so I highly doubt it was taken to be quickly developed and then ran into him again that night to sign. In my opinion I don’t think it’s genuine. I’m not a expert just my opinion.