Something I think that defined a lot of the reason behind Sonic's win, particularly in the Quan Chi match above is Erron's speed. All of the participants were quite strong and knew how to master their combos but Erron Black had so much speed over them and not in just the players reaction time but in his abilities and combat animations. Just watch Ketchup in particular, despite him proving capable of besting Erron in two seperate rounds he founds himself outmanoeuvred every time despite his reputation for amazing defence.
Though, in Ketchup's fault he should've changed variations you could see it wasn't working for him.
I'm not going to say Erron needs to be nerfed, no on the contrary. People need to reflect on these results and observe and spectate the character, so they can learn how to best it. For Erron? Perhaps someone fast could've bested him.
I would've loved to see Percect or Prodiginal fight Erron, as they might've been able to match him in speed but the closest to scratching him was M.I.T. Who played Scorpion, the fastest in front of Quan Chi and Jax.