I like it because it was about Goku not being the strongest. It was kinda like the original Dragon Ball episode where Master Roshi as Jackie Chun making it his mission to defeat Goku at the tournament so he would continue to get stronger and train his body to become even more powerful.
In the end of DBZ, Goku became the master of Uub, so, it kinda felt like Goku was unbeatable and boring now because he had to train Uub now so he could get a worthy challenge someday...maybe...
It just felt like a terrible ending that made Goku a lame unbeatable Superman clone. The only reason why Goku was so epic was because he fought Frieza, a character so powerful that he actually killed Goku, even as a super saiyan; he would have remained dead to if it wasn't for that wish to bring him back to life.
So to have Bills come in and beat Goku makes him human again...Or saiyan, whatever.
The point is a Hero isn't great unless he has a greater adversary. A hero is even greater when he dies if myths like Hercules haven't proven this point all ready before. This is probably what made Star Wars so good or Bardock the father of Goku, The history of Trunks, etc. When the good guy loses, we respect him.
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