I thought the whole 'massacre/adoption/fa mily' story was overdone.
Generally, i really like KFP2 (just a little less than I liked the first one).
But the whole origin/adopted/massacre story felt very forced, fake, and poorly executed.
One thing I liked about the first movie was the joke about Po not realizing that he's obviously adopted. It was sweet and showed his genuine love for his adopted father. Personally, I think this whole idea was covered adequately in the first film, but then they rehashed it and made it the focus of the sequel.
Which would have been fine if it was done well and wasn't overbearing. I liked the intro sequence very much, where it showed Shen killing the Pandas. Right in the very first minute of the movie, the entire origin of Po was already communicated to me. Shen killed the Pandas, they sent Po away (Moses style), and he was adopted by the goose.
I understood this in literally the first minute. There was no reason at all to keep coming back to this over and over, with something like 5 or 6 flashback sequences, telling me things I already know.
What they should have done is framed Po's conversation with his adopted father about his past in the light of Po becoming an adult, and the goose trying to hold on to his son. Goose's respect for his son would lead him to tell him about his true history.
Then later in the film, near the end, Po could learn that the Pandas were killed by Shen, giving him further motive to stop him. The flashbacks were totally unnecessary in my opinion.
Then I was totally stunned by the ending, which completely negates the previous development of Po. The movie establishes that Po comes from humble origins, has a genuine parental relationship with his adopted father, and became a Kung Fu Master through devotion and purity of character. It also shows the great sacrifice of the Panda parents, saving their son but dying themselves, and makes Po an instrument of POetic (couldn't resist) justice.
So why do they introduce psychic Panda-dad?! It makes no sense. This now brings Po's family back into question, a plot line that should be settled. It also makes Shen much less serious. What kind of a villain goes to massacre a village and lets, what, everyone get away? So now there's going to be lots of Pandas? This makes Po a much weaker character. Before, he was making his own destiny, now he's going to have to deal with a conflict of loyalty with a "family" he's never met.
It can only end two ways. A) Po has a new relationship with his father, discarding the previous message that a father doesn't have to be biological. B) He stays with his current father, rehashing a now 3 movie old plot line.
Either way continuing with a parental story prevents Po from becoming an adult character. He will now be relegated to a child role for another movie.
On another note, having ANOTHER Panda warrior will be boring and will make Po less unique.