To get top 25 on boss rush time, you need to beat it in 92 seconds or less? High scores have become a joke on this site, it's just a bunch of people that can't beat the game without hacking.
The glacier snake is the best pet for beating the last boss. It'll keep the boss distracted with its ranged attack, and will freeze him every few attacks.
I finally earned that badge. Now I never have to play this terrible game ever again. The AI and gameplay are so unbalanced, it's as much luck as skill for beating the computer. This makes it so frusterating to get to the 500 points needed to win all 7 quests.