for starters you have to analyze each captain. Komamura 7th Squad is probably the strongest captain in terms of unarmed physical combat. His Zanpakuto Tenken when shikai is activated anything he does forces an image of his Bankai Kukujou Tengen Myo-Oh to do whatever Komamura did IE sword slash downward the giants fist holding the sword does the same. Whereas Mayuri Kurotsuchi 12th Squad is considered by Shunsui Kyoraku to be the strongest and most proficient in Kido Combat. Mayuris Zanpakuto Ashisogi Jizou can paralyze the limbs it cuts so therefore if Komamura initiates Bankai all mayuri would have to do is cut into specific parts of the giant and Komamura would also suffer. Stab the arms no more swordplay. Stab the legs no mobility. So i'd say mayuri would win in that case. Now if it was