I'm not sure how Sawyer ranking worse than Ash in the Kalos League makes Greninja seem stronger, but okay. :/
Well Tierno's Pokemon weren't weak by any means. Blastoise one-shotted Slurpuff who tied to Goodra and Raichu defeated Aegislash who gave Pikachu serious trouble. And Mega Sceptile took them out without taking any damage, without breaking a sweat.
Ash×Serena- Amourshipping rules!
A match made in heaven!