2 simple ways to guarantee you win every week.
1. You need a pet that can do aoe heal to your whole team. For undercard fights, just pick the team which will not do any damage in the first round and save it for last, use this team to heal your other pet up again, when you are facing the 4 celestials, both the ox and the dragon will not do any damage in the first round, in fact the bird doesn't also, just heal and run and repeat.
2. There is an invincible team that can beat ALL 4 celestials 100% all the time, but it will just take a long time to do so. Get a 3X turkey team, use food comma to sleep your opponent, switch to your next turkey, normal attack, sleep again, switch, sleep, normal attack, sleep, switch, normal attack, sleep.......just be careful on one of the celestial (the bird as he will use the delfection on one of the round, but nonetheless you will able to beat them all without any issue). This is the dumbest and slowest way to beat the torney (the final 4 bosses) but it works 100% of the time.