So a "friend" in Canada sent me a tablet ( I think it was worth $400 U.S. currency) to replace the one I had that I could barely do anything on. I never asked for one, and I remember repeatedly that I told him not to get it for me, but he did. Now that I'm no longer in his life, he wants me to send back everything he sent me, and he says he will report the tablet as stolen if I don't return it. I know about conditional gifts, but I never made any promises tied to the tablet, so I'm not sure if it counts as a conditional gift.
If someone gave a gift than requested it back is it legal?
The request itself is legal, but that does not mean that you have to comply with it.
I never promised anything that tied to the tablet. So I'm not sure if it counts as a conditional gift.
It does not. An unconditional gift (which initially you did not even want) fails to meet the elements of a cognizable doctrine such as contract, promissory estoppel, fraud, or unjust enrichment.
he says he will report the tablet as stolen if I don't return it
He might get in trouble if he does that, since he knows or should know that the tablet was never stolen. He gave it away despite your initial refusal(s). As such, he might incur false reporting of a crime.