Chiro is the main protagonist of Super Robot Monkey Team Hyperforce Go!. Over the course of the series, he grows as a person and as a fighter, though uniquely compared to a majority of his contemporaries, Chiro actually starts the series already fairly adept at fighting.
Imagine Thanos without the Infinity Stones. No army. No armor. No weapon. Just full on fists against fists. Pick any fictional character from any franchise or studio that could take on Thanos in a fight. It's something I could have thought of long ago. THere will be a level two on fighting Thanos WITH a weapon. A level 3 with armor. A level 4 with an army. A level 5 of just Thanos with the Infinity Gauntlet. And a level 6 with everything. REMEMBER: only pick franchises that have characters CAPABLE of fighting.
