Just make the 16 that reached the Division Final ineligible for the next contest.
So that eliminates all of these characters from the nomination phase:
Mario vs. Bowser
Sonic vs. Dr. Robotnik
X vs. Zero
Sub-Zero vs. Scorpion
Pokemon Trainer Red vs. Blue
Ryu vs. Ken
Samus vs. Ridley
Big Boss vs. The Boss
Link vs. Ganondorf
Mega Man vs. Dr. Wily
Alucard vs. Dracula
Frog vs. Magus
Cloud vs. Sephiroth
Solid Snake vs. Liquid Snake
Squall vs. Seifer
Sora vs. Riku
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