If you're referring to Champions as in League Champions Ash battled;
Alder in Ash Versus the Champion! (BW052) (Alder forfeits)
Cynthia in Malice In Wonderland! (DP043) (Ash wins)
^This was actually just a dream caused by Mismagius but close enough :P technically battled
Drake in Hello, Pummelo! and Enter The Dragonite (Ash wins)
Champions as in Conference champions Ash has battled;
Tyson in Choose It or Lose It! and At The End of the Fray! (Ash loses)
Tobias in The Semi-Final Frontier! (Ash loses)
He has met all the other champions but never battled them.
