The Digivolution levels are as follows
Fresh - In-Training - Rookie - Champion - Ultimate - Mega
Champion is the fourth level and you are guaranteed to get one, as Digimon can only die at the Champion level unless you kill them on purpose with devil chips, something you are unable to get until the end of the game. Even if you don't manage to achieve the needed stats to get one of the Champion level Digimon on your Digimon's list, your Digimon will Digivolve into either Numemon (higher strength) or Geremon (Higher Intelligence) meaning that no matter what you do, you will get a Champion level partner.